w3schoolworld: 2016

Wednesday, 2 November 2016

PHP 5 Constants

PHP 5 Constants

Constants are like variables except that once they are defined they cannot be changed or undefined.

PHP Constants
A constant is an identifier (name) for a simple value. The value cannot be changed during the script.

A valid constant name starts with a letter or underscore (no $ sign before the constant name).

Note: Unlike variables, constants are automatically global across the entire script.

Create a PHP Constant
To create a constant, use the define() function.

Syntax
define(name, value, case-insensitive)
Parameters:

name: Specifies the name of the constant
value: Specifies the value of the constant
case-insensitive: Specifies whether the constant name should be case-insensitive. Default is false
The example below creates a constant with a case-sensitive name:

Example
<?php
define("GREETING", "Welcome to W3Schoolworld.com!");
echo GREETING;
?>

The example below creates a constant with a case-insensitive name:

Example
<?php
define("GREETING", "Welcome to W3Schoolworld.com!", true);
echo greeting;
?>

Constants are Global
Constants are automatically global and can be used across the entire script.

The example below uses a constant inside a function, even if it is defined outside the function:

Example
<?php
define("GREETING", "Welcome to W3Schoolworld.com!");

function myTest() {
echo GREETING;
}

myTest();
?>

Sunday, 9 October 2016

PHP String Functions

PHP String Functions
In this chapter we will look at some commonly used functions to manipulate strings.

Get The Length of a String
The PHP strlen() function returns the length of a string.

The example below returns the length of the string "Hello w3schoolworld!":

Example
<?php
echo strlen("Hello w3schoolworld!"); // outputs 20
?>

The output of the code above will be: 20.

Count The Number of Words in a String
The PHP str_word_count() function counts the number of words in a string:

Example
<?php
echo str_word_count("Hello w3schoolworld!"); // outputs 2
?>

The output of the code above will be: 2.

Reverse a String
The PHP strrev() function reverses a string:

Example
<?php
echo strrev("Hello world!"); // outputs !dlrow olleH
?>

The output of the code above will be: !dlrow olleH.

Search For a Specific Text Within a String
The PHP strpos() function searches for a specific text within a string.

If a match is found, the function returns the character position of the first match. If no match is found, it will return FALSE.

The example below searches for the text "world" in the string "Hello world"

Example

<?php
echo strpos("Hello world!", "world"); // outputs 6
?>

The output of the code above will be: 6.

Tip: The first character position in a string is 0 (not 1).

Replace Text Within a String
The PHP str_replace() function replaces some characters with some other characters in a string.

The example below replaces the text "world" with "Dolly":

Example
<?php
echo str_replace("world", "Dolly", "Hello world!"); // outputs Hello Dolly!
?>

The output of the code above will be: Hello Dolly!

Complete PHP String Reference
For a complete reference of all string functions, go to our complete PHP String Reference.

The PHP string reference contains description and example of use, for each function!

PHP Data Types

PHP Data Types
Variables can store data of different types, and different data types can do different things.

PHP supports the following data types:

String
Integer
Float (floating point numbers - also called double)
Boolean
Array
Object
NULL
Resource
PHP String
A string is a sequence of characters, like "Hello world!".

A string can be any text inside quotes. You can use single or double quotes:

Example
<?php
$x = "Hello world!";
$y = 'Hello world!';

echo $x;
echo "<br>";
echo $y;
?>

PHP Integer
An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647.

Rules for integers:

An integer must have at least one digit
An integer must not have a decimal point
An integer can be either positive or negative
Integers can be specified in three formats: decimal (10-based), hexadecimal (16-based - prefixed with 0x) or octal (8-based - prefixed with 0)
In the following example $x is an integer. The PHP var_dump() function returns the data type and value:

Example
<?php
$x = 5985;
var_dump($x);
?>

PHP Float
A float (floating point number) is a number with a decimal point or a number in exponential form.

In the following example $x is a float. The PHP var_dump() function returns the data type and value:

Example
<?php
$x = 10.365;
var_dump($x);
?>

PHP Boolean
A Boolean represents two possible states: TRUE or FALSE.

$x = true;
$y = false;
Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial.

PHP Array
An array stores multiple values in one single variable.

In the following example $cars is an array. The PHP var_dump() function returns the data type and value:

Example
<?php
$cars = array("Volvo","BMW","Toyota");
var_dump($cars);
?>

You will learn a lot more about arrays in later chapters of this tutorial.

PHP Object
An object is a data type which stores data and information on how to process that data.

In PHP, an object must be explicitly declared.

First we must declare a class of object. For this, we use the class keyword. A class is a structure that can contain properties and methods:

Example
<?php
class Car {
    function Car() {
        $this->model = "VW";
    }
}

// create an object
$herbie = new Car();

// show object properties
echo $herbie->model;
?>

You will learn more about objects in a later chapter of this tutorial.

PHP NULL Value
Null is a special data type which can have only one value: NULL.

A variable of data type NULL is a variable that has no value assigned to it.

Tip: If a variable is created without a value, it is automatically assigned a value of NULL.

Variables can also be emptied by setting the value to NULL:

Example
<?php
$x = "Hello world!";
$x = null;
var_dump($x);
?>

PHP Resource
The special resource type is not an actual data type. It is the storing of a reference to functions and resources external to PHP.

A common example of using the resource data type is a database call.

We will not talk about the resource type here, since it is an advanced topic.

how use PHP 5 echo and print Statements

PHP 5 echo and print Statements

In PHP there are two basic ways to get output: echo and print.

In this tutorial we use echo (and print) in almost every example. So, this chapter contains a little more info about those two output statements.

PHP echo and print Statements
echo and print are more or less the same. They are both used to output data to the screen.

The differences are small: echo has no return value while print has a return value of 1 so it can be used in expressions. echo can take multiple parameters (although such usage is rare) while print can take one argument. echo is marginally faster than print.

The PHP echo Statement
The echo statement can be used with or without parentheses: echo or echo().

Display Text

The following example shows how to output text with the echo command (notice that the text can contain HTML markup):

Example
<?php
echo "<h2>PHP is Fun!</h2>";
echo "Hello world!<br>";
echo "I'm about to learn PHP!<br>";
echo "This ", "string ", "was ", "made ", "with multiple parameters.";
?>

Display Variables

The following example shows how to output text and variables with the echo statement:

Example
<?php
$txt1 = "Learn PHP";
$txt2 = "W3Schoolworld.com";
$x = 5;
$y = 4;

echo "<h2>$txt1</h2>";
echo "Study PHP at $txt2<br>";
echo $x + $y;
?>

The PHP print Statement
The print statement can be used with or without parentheses: print or print().

Display Text

The following example shows how to output text with the print command (notice that the text can contain HTML markup):

Example
<?php
print "<h2>PHP is Fun!</h2>";
print "Hello world!<br>";
print "I'm about to learn PHP!";
?>

Display Variables

The following example shows how to output text and variables with the print statement:

Example
<?php
$txt1 = "Learn PHP";
$txt2 = "W3Schoolworld.com";
$x = 5;
$y = 4;

print "<h2>$txt1</h2>";
print "Study PHP at $txt2<br>";
print $x + $y;
?>

Creating (Declaring) PHP Variables

Creating (Declaring) PHP Variables

In PHP, a variable starts with the $ sign, followed by the name of the variable:

Example
<?php
$txt = "Hello world!";
$x = 5;
$y = 10.5;
?>

PHP Variables
A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume).

Rules for PHP variables:

A variable starts with the $ sign, followed by the name of the variable
A variable name must start with a letter or the underscore character
A variable name cannot start with a number
A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
Variable names are case-sensitive ($age and $AGE are two different variables)
Remember that PHP variable names are case-sensitive!

Output Variables
The PHP echo statement is often used to output data to the screen.

The following example will show how to output text and a variable:

Example
<?php
$txt = "W3Schoolworld.com";
echo "I love $txt!";
?>

The following example will produce the same output as the example above:

Example
<?php
$txt = "W3Schoolworld.com";
echo "I love " . $txt . "!";
?>

The following example will output the sum of two variables:

Example
<?php
$x = 5;
$y = 4;
echo $x + $y;
?>

Note: You will learn more about the echo statement and how to output data to the screen in the next chapter.

PHP is a Loosely Typed Language
In the example above, notice that we did not have to tell PHP which data type the variable is.

PHP automatically converts the variable to the correct data type, depending on its value.

In other languages such as C, C++, and Java, the programmer must declare the name and type of the variable before using it.

PHP Variables Scope
In PHP, variables can be declared anywhere in the script.

The scope of a variable is the part of the script where the variable can be referenced/used.

PHP has three different variable scopes:

local
global
static

Global and Local Scope
A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function:

Example
<?php
$x = 5; // global scope

function myTest() {
// using x inside this function will generate an error
echo "<p>Variable x inside function is: $x</p>";
}
myTest();

echo "<p>Variable x outside function is: $x</p>";
?>

A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function:

Example
<?php
function myTest() {
$x = 5; // local scope
echo "<p>Variable x inside function is: $x</p>";
}
myTest();

// using x outside the function will generate an error
echo "<p>Variable x outside function is: $x</p>";
?>

You can have local variables with the same name in different functions, because local variables are only recognized by the function in which they are declared.

PHP The global Keyword
The global keyword is used to access a global variable from within a function.

To do this, use the global keyword before the variables (inside the function):

Example
<?php
$x = 5;
$y = 10;

function myTest() {
global $x, $y;
$y = $x + $y;
}

myTest();
echo $y; // outputs 15
?>

PHP also stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable. This array is also accessible from within functions and can be used to update global variables directly.

The example above can be rewritten like this:

Example
<?php
$x = 5;
$y = 10;

function myTest() {
$GLOBALS['y'] = $GLOBALS['x'] + $GLOBALS['y'];
}

myTest();
echo $y; // outputs 15
?>

PHP The static Keyword
Normally, when a function is completed/executed, all of its variables are deleted. However, sometimes we want a local variable NOT to be deleted. We need it for a further job.

To do this, use the static keyword when you first declare the variable:

Example
<?php
function myTest() {
    static $x = 0;
    echo $x;
    $x++;
}

myTest();
myTest();
myTest();
?>

Then, each time the function is called, that variable will still have the information it contained from the last time the function was called.

Note: The variable is still local to the function.

Creating (Declaring) PHP Variables

Creating (Declaring) PHP Variables

In PHP, a variable starts with the $ sign, followed by the name of the variable:

Example
<?php
$txt = "Hello world!";
$x = 5;
$y = 10.5;
?>

PHP Variables
A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume).

Rules for PHP variables:

Output Variables
The PHP echo statement is often used to output data to the screen.

The following example will show how to output text and a variable:

Example
<?php
$txt = "W3Schoolworld.com";
echo "I love $txt!";
?>

The following example will produce the same output as the example above:

Example
<?php
$txt = "W3Schoolworld.com";
echo "I love " . $txt . "!";
?>

The following example will output the sum of two variables:

Example
<?php
$x = 5;
$y = 4;
echo $x + $y;
?>

Note: You will learn more about the echo statement and how to output data to the screen in the next chapter.

PHP is a Loosely Typed Language
In the example above, notice that we did not have to tell PHP which data type the variable is.

PHP automatically converts the variable to the correct data type, depending on its value.

In other languages such as C, C++, and Java, the programmer must declare the name and type of the variable before using it.

PHP Variables Scope
In PHP, variables can be declared anywhere in the script.

The scope of a variable is the part of the script where the variable can be referenced/used.

PHP has three different variable scopes:

local
global
static

Global and Local Scope
A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function:

Example
<?php
$x = 5; // global scope

function myTest() {
// using x inside this function will generate an error
echo "<p>Variable x inside function is: $x</p>";
}
myTest();

echo "<p>Variable x outside function is: $x</p>";
?>

A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function:

Example
<?php
function myTest() {
$x = 5; // local scope
echo "<p>Variable x inside function is: $x</p>";
}
myTest();

// using x outside the function will generate an error
echo "<p>Variable x outside function is: $x</p>";
?>

You can have local variables with the same name in different functions, because local variables are only recognized by the function in which they are declared.

PHP The global Keyword
The global keyword is used to access a global variable from within a function.

To do this, use the global keyword before the variables (inside the function):

Example
<?php
$x = 5;
$y = 10;

function myTest() {
global $x, $y;
$y = $x + $y;
}

myTest();
echo $y; // outputs 15
?>

The example above can be rewritten like this:

Example
<?php
$x = 5;
$y = 10;

function myTest() {
$GLOBALS['y'] = $GLOBALS['x'] + $GLOBALS['y'];
}

myTest();
echo $y; // outputs 15
?>

PHP The static Keyword
Normally, when a function is completed/executed, all of its variables are deleted. However, sometimes we want a local variable NOT to be deleted. We need it for a further job.

To do this, use the static keyword when you first declare the variable:

Example
<?php
function myTest() {
    static $x = 0;
    echo $x;
    $x++;
}

myTest();
myTest();
myTest();
?>

Then, each time the function is called, that variable will still have the information it contained from the last time the function was called.

Note: The variable is still local to the function.

how use Comments in PHP

Comments in PHP
A comment in PHP code is a line that is not read/executed as part of the program. Its only purpose is to be read by someone who is looking at the code.

Comments can be used to:

Let others understand what you are doing
Remind yourself of what you did - Most programmers have experienced coming back to their own work a year or two later and having to re-figure out what they did. Comments can remind you of what you were thinking when you wrote the code
PHP supports several ways of commenting:

Example
<!DOCTYPE html>
<html>
<body>

<?php
// This is a single-line comment

# This is also a single-line comment

/*
This is a multiple-lines comment block
that spans over multiple
lines
*/

// You can also use comments to leave out parts of a code line
$x = 5 /* + 15 */ + 5;
echo $x;
?>

</body>
</html>

PHP Case Sensitivity
In PHP, all keywords (e.g. if, else, while, echo, etc.), classes, functions, and user-defined functions are NOT case-sensitive.

In the example below, all three echo statements below are legal (and equal):

Example
<!DOCTYPE html>
<html>
<body>

<?php
ECHO "Hello World!<br>";
echo "Hello World!<br>";
EcHo "Hello World!<br>";
?>

</body>
</html>

However; all variable names are case-sensitive.

In the example below, only the first statement will display the value of the $color variable (this is because $color, $COLOR, and $coLOR are treated as three different variables):

Example
<!DOCTYPE html>
<html>
<body>

<?php
$color = "red";
echo "My car is " . $color . "<br>";
echo "My house is " . $COLOR . "<br>";
echo "My boat is " . $coLOR . "<br>";
?>

</body>
</html>

Basic PHP Syntax

A PHP script is executed on the server, and the plain HTML result is sent back to the browser.

Basic PHP Syntax
A PHP script can be placed anywhere in the document.

A PHP script starts with <?php and ends with ?>:

<?php
// PHP code goes here
?>
The default file extension for PHP files is ".php".

A PHP file normally contains HTML tags, and some PHP scripting code.

Below, we have an example of a simple PHP file, with a PHP script that uses a built-in PHP function "echo" to output the text "Hello World!" on a web page:

Example
<!DOCTYPE html>
<html>
<body>

<h1>My first PHP page example</h1>

<?php
echo "Hello w3schoolWorld!";
?>

</body>
</html>

PHP 5 how Install??

What Do I Need?
To start using PHP, you can:

Find a web host with PHP and MySQL support
Install a web server on your own PC, and then install PHP and MySQL
Use a Web Host With PHP Support
If your server has activated support for PHP you do not need to do anything.

Just create some .php files, place them in your web directory, and the server will automatically parse them for you.

You do not need to compile anything or install any extra tools.

Because PHP is free, most web hosts offer PHP support.

Set Up PHP on Your Own PC
However, if your server does not support PHP, you must:

install a web server
install PHP
install a database, such as MySQL
The official PHP website (PHP.net) has installation instructions for PHP: http://php.net/manual/en/install.php

Friday, 29 April 2016

Html attributes

w3schoolworld

HTML Attributes.

HTML elements can have attributes
Attributes provide additional information about an element
Attributes are always specified in the start tag
Attributes come in name/value pairs like: name="value"

The lang Attribute

The document language can be declared in the <html> tag.

The language is declared in the lang attribute.

Declaring a language is important for accessibility applications (screen readers) and search engines:

<!DOCTYPE html>
<html lang="en-US">
<body>

<h1>My First Heading</h1>
<p>My first paragraph.</p>

</body>
</html>

The title Attribute

HTML paragraphs are defined with the <p> tag.

In this example, the <p> element has a title attribute. The value of the attribute is "About amegingthoughts":

<p title="About amegingthought">
Amegingthought is a web developer's site.
It provides tutorials and references covering
many aspects of web programming,
including HTML, CSS, JavaScript, XML, SQL, PHP, ASP, etc.
</p>

The href Attribute

HTML links are defined with the <a> tag. The link address is specified in the href attribute:

Size Attributes

HTML images are defined with the <img> tag.

The filename of the source (src), and the size of the image (width and height) are all provided as attributes:

The alt Attribute

The alt attribute specifies an alternative text to be used, when an HTML element cannot be displayed.

The value of the attribute can be read by "screen readers". This way, someone "listening" to the webpage, i.e. a blind person, can "hear" the element.

We Suggest: Always Use Lowercase Attributes

The HTML5 standard does not require lower case attribute names.

The title attribute can be written with upper or lower case like Title and/or TITLE.

W3Cw recommends lowercase in HTML4, and demands lowercase for stricter document types like XHTML.

We Suggest: Always Quote Attribute Values

The HTML5 standard does not require quotes around attribute values.

The href attribute, demonstrated above, can be written as:

W3C recommends quotes in HTML4, and demands quotes for stricter document types like XHTML.

Sometimes it is necessary to use quotes. This will not display correctly, because it contains a space:

Single or Double Quotes?.

Double style quotes are the most common in HTML, but single style can also be used.

In some situations, when the attribute value itself contains double quotes, it is necessary to use single quotes:

Chapter Summary

All HTML elements can have attributes
The HTML title attribute provides additional "tool-tip" information
The HTML href attribute provides address information for links
The HTML width and height attributes provide size information for images
The HTML alt attribute provides text for screen readers
At W3Schoolworld we always use lowercase HTML attribute names
At W3Schoolworld we always quote attributes with double quotes

Html comment tags

w3schoolworld

HTML Comment Tags

<p>This is a paragraph.</p>

Conditional Comments

Software Program Tags.

HTML comments tags can also be generated by various HTML software programs.

For example  tags wrapped inside HTML comments by FrontPage and Expression Web.

As a rule, let these tags stay, to help support the software that created them.

Html computer code elements

w3schoolworld

HTML Computer Code Elements

<code>
var x = 5;
var y = 6;
document.getElementById("demo").innerHTML = x + y;
</code>

HTML Computer Code Formatting

HTML normally uses variable letter size and spacing.

This is not wanted when displaying examples of computer code.

The <kbd>, <samp>, and <code> elements all support fixed letter size and spacing.

HTML <kbd> For Keyboard Input.

The HTML <kbd> element defines keyboard input:

HTML <samp> For Computer Output

The HTML <samp> element defines sample output from a computer program:

<samp>
demo.example.com login: Apr 12 09:10:17
Linux 2.6.10-grsec+gg3+e+fhs6b+nfs+gr0501+++p3+c4a+gr2b-reslog-v6.189
</samp>

HTML <code> For Computer Code

The HTML <code> element defines a piece of programming code:

<code>
var x = 5;
var y = 6;
document.getElementById("demo").innerHTML = x + y;
</code>

Notice that the <code> element does not preserve extra whitespace and line-breaks.

To fix this, you can put the <code> element inside a <pre> element:

<pre>
<code>
var x = 5;
var y = 6;
document.getElementById("demo").innerHTML = x + y;
</code>
</pre>

HTML <var> For Variables

The HTML <var> element defines a variable.

The variable could be a variable in a mathematical expression or a variable in programming context:

Einstein wrote: <var>E</var> = <var>m</var><var>c</var><sup>2</sup>.

HTML Computer Code Elements

<code>Defines programming code
<kbd>Defines keyboard input
<samp>Defines computer output
<var>Defines a variable
<pre>Defines preformatted text

Html quotation and citation elements

w3schoolworld

HTML Quotation and Citation Elements

Here is a quote from WWF's website:

For 50 years, WWF has been protecting the future of nature. The world's leading conservation organization, WWF works in 100 countries and is supported by 1.2 million members in the United States and close to 5 million globally.

HTML <q> for Short Quotations

The HTML <q> element defines a short quotation.

Browsers usually insert quotation marks around the <q> element.

<p>WWF's goal is to: <q>Build a future where people live in harmony with nature.</q></p>

HTML <blockquote> for Long Quotations

The HTML <blockquote> element defines a quoted section.

Browsers usually indent <blockquote> elements.

<p>Here is a quote from WWF's website:</p>
<blockquote cite="http://www.wildlife.org/who/index.html">
For 50 years, WWF has been protecting the future of nature.
The world's leading conservation organization,
WWF works in 100 countries and is supported by
1.2 million members in the United States and
close to 5 million globally.
</blockquote>

HTML <abbr> for Abbreviations

The HTML <abbr> element defines an abbreviation or an acronym.

Marking abbreviations can give useful information to browsers, translation systems and search-engines.

<p>The <abbr title="World Health Organization">WHO</abbr> was founded in 1948.</p>

HTML <address> for Contact Information

The HTML <address> element defines contact information (author/owner) of a document or article.

The <address> element is usually displayed in italic. Most browsers will add a line break before and after the element.

<address>
Written by Jon Doe.<br>
Visit us at:<br>
Example.com<br>
Box 564, Disneyland<br>
USA
</address>

HTML <cite> for Work Title

The HTML <cite> element defines the title of a work.

Browsers usually display <cite> elements in italic.

<p><cite>The Scream</cite> by Edward Munch. Painted in 1893.</p>

HTML <bdo> for Bi-Directional Override

The HTML <bdo> element defines bi-directional override.

The <bdo> element is used to override the current text direction:

<bdo dir="rtl">This text will be written from right to left</bdo>

HTML Quotation and Citation Elements

<abbr>Defines an abbreviation or acronym
<address>Defines contact information for the author/owner of a document
<bdo>Defines the text direction
<blockquote>Defines a section that is quoted from another source
<cite>Defines the title of a work
<q>Defines a short inline quotation

Html formatting elements

w3schoolworld

HTML Formatting Elements

In the previous chapter, you learned about HTML styling, using the HTML style attribute.

HTML also defines special elements, for defining text with a special meaning.

HTML uses elements like <b> and <i> for formatting output, like bold or italic text.

Formatting elements were designed to display special types of text:

Bold text
Important text
Italic text
Emphasized text
Marked text
Small text
Deleted text
Inserted text
Subscripts
Superscripts

HTML Bold and Strong Formatting

The HTML <b> element defines bold text, without any extra importance.

<p>This text is normal.</p>

The HTML <strong> element defines strong text, with added semantic "strong" importance.

<p>This text is normal.</p>

<p><strong>This text is strong</strong>.</p>

HTML Italic and Emphasized Formatting.

The HTML <i> element defines italic text, without any extra importance.

<p>This text is normal.</p>

<p><i>This text is italic</i>.</p>

The HTML <em> element defines emphasized text, with added semantic importance.

<p>This text is normal.</p>

<p><em>This text is emphasized</em>.</p>

HTML Small Formatting

The HTML <small> element defines small text:

<h2>HTML <small>Small</small> Formatting</h2>

HTML Marked Formatting

The HTML <mark> element defines marked or highlighted text:

<h2>HTML <mark>Marked</mark> Formatting</h2>

HTML Deleted Formatting

The HTML <del> element defines deleted (removed) text.

<p>My favorite color is <del>blue</del> red.</p>

HTML Inserted Formatting.

The HTML <ins> element defines inserted (added) text.

<p>My favorite <ins>color</ins> is red.</p>

HTML Subscript Formatting

The HTML <sub> element defines subscripted text.

<p>This is <sub>subscripted</sub> text.</p>

HTML Superscript Formatting

The HTML <sup> element defines superscripted text.

<p>This is <sup>superscripted</sup> text.</p>

HTML Text Formatting Elements

<b>Defines bold text
<em>Defines emphasized text
<i>Defines italic text
<small>Defines smaller text
<strong>Defines important text
<sub>Defines subscripted text
<sup>Defines superscripted text
<ins>Defines inserted text
<del>Defines deleted text
<mark>Defines marked/highlighted text

Html style attribute

w3schoolworld

The HTML Style Attribute

Setting the style of an HTML element, can be done with the style attribute.

The HTML style attribute has the following syntax:

style="property:value;"

HTML Background Color

The background-color property defines the background color for an HTML element:

This example sets the background for a page to lightgrey:

<h1>This is a heading</h1>
<p>This is a paragraph.</p>

</body>

HTML Text Color.

The color property defines the text color for an HTML element:

<h1 style="color:blue;">This is a heading</h1>
<p style="color:red;">This is a paragraph.</p>

HTML Fonts

The font-family property defines the font to be used for an HTML element:

<h1 style="font-family:verdana;">This is a heading</h1>
<p style="font-family:courier;">This is a paragraph.</p>

HTML Text Size.

The font-size property defines the text size for an HTML element:

<h1 style="font-size:300%;">This is a heading</h1>
<p style="font-size:160%;">This is a paragraph.</p>

HTML Text Alignment

The text-align property defines the horizontal text alignment for an HTML element:

<h1 style="text-align:center;">Centered Heading</h1>
<p>This is a paragraph.</p>

Chapter Summary

Use the style attribute for styling HTML elements
Use background-color for background color
Use color for text colors
Use font-family for text fonts
Use font-size for text sizes
Use text-align for text alignment

Html paragraphs

w3schoolworld

HTML Paragraphs

The HTML <p> element defines a paragraph.

<p>This is a paragraph</p>
<p>This is another paragraph</p>

HTML Display

You cannot be sure how HTML will be displayed.

Large or small screens, and resized windows will create different results.

With HTML, you cannot change the output by adding extra spaces or extra lines in your HTML code.

The browser will remove extra spaces and extra lines when the page is displayed.

Any number of spaces, and any number of new lines, count as only one space.

<p>
This paragraph
contains a lot of lines
in the source code,
but the browser
ignores it.
</p>

<p>
This paragraph
contains a lot of spaces
in the source code,
but the browser
ignores it.
</p>

Don't Forget the End Tag.

Most browsers will display HTML correctly even if you forget the end tag:

<p>This is a paragraph
<p>This is another paragraph

HTML Line Breaks

The HTML <br> element defines a line break.

Use <br> if you want a line break (a new line) without starting a new paragraph:

<p>This is<br>a para<br>graph with line breaks</p>

The Poem Problem

<p>This poem will display as one line:</p>
<p>
My Bonnie lies over the ocean.

My Bonnie lies over the sea.

My Bonnie lies over the ocean.

Oh, bring back my Bonnie to me.
</p>

The HTML <pre> Element

The HTML <pre> element defines preformatted text.

The text inside a <pre> element is displayed in a fixed-width font (usually Courier), and it preserves both spaces and line breaks:

<pre>
My Bonnie lies over the ocean.

My Bonnie lies over the sea.

My Bonnie lies over the ocean.

Oh, bring back my Bonnie to me.
</pre>

HTML Tag Reference.

W3Schools' tag reference contains additional information about HTML elements and their attributes.

<p>Defines a paragraph
<br>Inserts a single line break
<pre>Defines pre-formatted text

Html heading

w3schoolworld

HTML Headings

Headings are defined with the <h1> to <h6> tags.

<h1> defines the most important heading. <h6> defines the least important heading.

<h1>This is a heading</h1>
<h2>This is a heading</h2>
<h3>This is a heading</h3>

Headings Are Important

Use HTML headings for headings only. Don't use headings to make text BIG or bold.

Search engines use your headings to index the structure and content of your web pages.

Users skim your pages by its headings. It is important to use headings to show the document structure.

h1 headings should be main headings, followed by h2 headings, then the less important h3, and so on.

HTML Horizontal Rules.

The <hr> tag creates a horizontal line in an HTML page.

The hr element can be used to separate content:

<p>This is a paragraph.</p>
<hr>
<p>This is a paragraph.</p>
<hr>
<p>This is a paragraph.</p>

The HTML <head> Element

The HTML <head> element has nothing to do with HTML headings.

The HTML <head> element contains meta data. Meta data are not displayed.

The HTML <head> element is placed between the <html> tag and the <body> tag:

<!DOCTYPE html>
<html>

<head>
<title>My First HTML</title>
<meta charset="UTF-8">
</head>

<body>
.
.
.

The HTML <title> Element.

The HTML <title> element is meta data. It defines the HTML document's title.

The title will not be displayed in the document, but might be displayed in the browser tab.

The HTML <meta> Element

The HTML <meta> element is also meta data.

It can be used to define the character set, and other information about the HTML document.

More Meta Elements.

In the chapter about HTML styles you discover more meta elements:

The HTML <style> element is used to define internal CSS style sheets.

The HTML <link> element is used to define external CSS style sheets.

HTML Tip - How to View HTML Source

Have you ever seen a Web page and wondered "Hey! How did they do that?"

To find out, right-click in the page and select "View Page Source" (in Chrome) or "View Source" (in IE), or similar in another browser. This will open a window containing the HTML code of the page.

HTML Tag Reference.

W3Schools' tag reference contains additional information about these tags and their attributes.

You will learn more about HTML tags and attributes in the next chapters of this tutorial.

<html>Defines an HTML document
<body>Defines the document's body
<head> Defines the document's head element
<h1> to <h6>Defines HTML headings
<hr>Defines a horizontal line

Html attributes

HTML

HTML Attributes.

HTML elements can have attributes
Attributes provide additional information about an element
Attributes are always specified in the start tag
Attributes come in name/value pairs like: name="value"

The lang Attribute

The document language can be declared in the <html> tag.

The language is declared in the lang attribute.

Declaring a language is important for accessibility applications (screen readers) and search engines:

<!DOCTYPE html>
<html lang="en-US">
<body>

<h1>My First Heading</h1>
<p>My first paragraph.</p>

</body>
</html>

The title Attribute

HTML paragraphs are defined with the <p> tag.

In this example, the <p> element has a title attribute. The value of the attribute is "About amegingthoughts":

The href Attribute

HTML links are defined with the <a> tag. The link address is specified in the href attribute:

Size Attributes

HTML images are defined with the <img> tag.

The filename of the source (src), and the size of the image (width and height) are all provided as attributes:

The alt Attribute

The alt attribute specifies an alternative text to be used, when an HTML element cannot be displayed.

The value of the attribute can be read by "screen readers". This way, someone "listening" to the webpage, i.e. a blind person, can "hear" the element.

We Suggest: Always Use Lowercase Attributes

The HTML5 standard does not require lower case attribute names.

The title attribute can be written with upper or lower case like Title and/or TITLE.

W3C recommends lowercase in HTML4, and demands lowercase for stricter document types like XHTML.

We Suggest: Always Quote Attribute Values

The HTML5 standard does not require quotes around attribute values.

The href attribute, demonstrated above, can be written as:

W3C recommends quotes in HTML4, and demands quotes for stricter document types like XHTML.

Sometimes it is necessary to use quotes. This will not display correctly, because it contains a space:

Single or Double Quotes?.

Double style quotes are the most common in HTML, but single style can also be used.

In some situations, when the attribute value itself contains double quotes, it is necessary to use single quotes:

Chapter Summary

All HTML elements can have attributes
The HTML title attribute provides additional "tool-tip" information
The HTML href attribute provides address information for links
The HTML width and height attributes provide size information for images
The HTML alt attribute provides text for screen readers
At W3Schools we always use lowercase HTML attribute names
At W3Schools we always quote attributes with double quotes

Html elements learn

w3schoolworld

HTML Elements

HTML elements are written with a start tag, with an end tag, with the content in between:

<tagname>content</tagname>
The HTML element is everything from the start tag to the end tag:

<p>My first HTML paragraph.</p>

Nested HTML Elements

HTML elements can be nested (elements can contain elements).

All HTML documents consist of nested HTML elements.

This example contains 4 HTML elements:

<!DOCTYPE html>
<html>
<body>

<h1>My First Heading</h1>
<p>My first paragraph.</p>

</body>
</html>

HTML Example Explained

The <html> element defines the whole document.

It has a start tag <html> and an end tag </html>.

The element content is another HTML element (the <body> element).

<h1>My First Heading</h1>
<p>My first paragraph.</p>

</body>
</html>

The <body> element defines the document body.

It has a start tag <body> and an end tag </body>.

The element content is two other HTML elements (<h1> and <p>).

<body>

<h1>My First Heading</h1>
<p>My first paragraph.</p>

</body>

The <h1> element defines a heading.

It has a start tag <h1> and an end tag </h1>.

The element content is: My First Heading.

<h1>My First Heading</h1>

The <p> element defines a paragraph.

It has a start tag <p> and an end tag </p>.

The element content is: My first paragraph.

<p>My first paragraph.</p>

Don't Forget the End Tag

<p>This is a paragraph
<p>This is a paragraph

</body>
</html>

Empty HTML Elements.

HTML elements with no content are called empty elements.

<br> is an empty element without a closing tag (the <br> tag defines a line break).

Empty elements can be "closed" in the opening tag like this: <br />.

HTML5 does not require empty elements to be closed. But if you want stricter validation, or you need to make your document readable by XML parsers, you should close all HTML elements.

HTML Tip: Use Lowercase Tags

HTML tags are not case sensitive: <P> means the same as <p>.

The HTML5 standard does not require lowercase tags, but W3C recommends lowercase in HTML4, and demands lowercase for stricter document types like XHTML.

Html basic examples

w3schoolworld

HTML Documents

All HTML documents must start with a type declaration: <!DOCTYPE html>.

The HTML document itself begins with <html> and ends with </html>.

The visible part of the HTML document is between <body> and </body>.

<!DOCTYPE html>
<html>
<body>

<h1>My First Heading</h1>

<p>My first paragraph.</p>

</body>
</html>

HTML Headings

<h1>This is a heading</h1>
<h2>This is a heading</h2>
<h3>This is a heading</h3>

HTML Paragraphs

<p>This is a paragraph.</p>
<p>This is another paragraph.</p>

HTML Links

HTML Images

HTML images are defined with the <img> tag.

The source file (src), alternative text (alt), and size (width and height) are provided as attributes:

Learn html editor

Write HTML Using Notepad or TextEdit

HTML can be edited by using professional HTML editors like:

Microsoft WebMatrix
Sublime Text
However, for learning HTML we recommend a text editor like Notepad (PC) or TextEdit (Mac).

We believe using a simple text editor is a good way to learn HTML.

Follow the 4 steps below to create your first web page with Notepad.

Step 1: Open Notepad

To open Notepad in Windows 7 or earlier:

Click Start (bottom left on your screen). Click All Programs. Click Accessories. Click Notepad.

To open Notepad in Windows 8 or later:

Open the Start Screen (the window symbol at the bottom left on your screen). Type Notepad.

Step 2: Write Some HTML

<!DOCTYPE html>
<html>
<body>

<h1>My First Heading</h1>

<p>My first paragraph.</p>

</body>
</html>

Step 3: Save the HTML Page

Save the file on your computer.

Select File > Save as in the Notepad menu.

Name the file "index.html" or any other name ending with html or htm.

UTF-8 is the preferred encoding for HTML files.

ANSI encoding covers US and Western European characters only.

Step 4: View HTML Page in Your Browser

What is Bootstrap?

Bootstrap is a CSS framework for designing better web pages

Bootstrap is a free front-end framework for faster and easier web development
Bootstrap includes HTML and CSS based design templates for typography, forms, buttons, tables, navigation, modals, image carousels and many other, as well as optional JavaScript plugins
Bootstrap also gives you the ability to easily create responsive designs

Bootstrap 3 Tutorial

Bootstrap is the most popular HTML, CSS, and JavaScript framework for developing responsive, mobile-first web sites.

Why Use Bootstrap?

Easy to use: Anybody with just basic knowledge of HTML and CSS can start using Bootstrap
Responsive features: Bootstrap's responsive CSS adjusts to phones, tablets, and desktops
Mobile-first approach: In Bootstrap 3, mobile-first styles are part of the core framework
Browser compatibility: Bootstrap is compatible with all modern browsers (Chrome, Firefox, Internet Explorer, Safari, and

What is SQL?

A language for accessing databases

SQL stands for Structured Query Language
SQL lets you access and manipulate databases
SQL is an ANSI (American National Standards Institute) standard

What is SQL?

SQL stands for Structured Query Language
SQL lets you access and manipulate databases
SQL is an ANSI (American National Standards Institute) standard

What Can SQL do?

SQL can execute queries against a database
SQL can retrieve data from a database
SQL can insert records in a database
SQL can update records in a database
SQL can delete records from a database
SQL can create new databases
SQL can create new tables in a database
SQL can create stored procedures in a database
SQL can create views in a database
SQL can set permissions on tables, procedures, and views

What is jQuery?

A JavaScript library for developing web pages

jQuery is a lightweight, "write less, do more", JavaScript library.

The purpose of jQuery is to make it much easier to use JavaScript on your website.

jQuery takes a lot of common tasks that require many lines of JavaScript code to accomplish, and wraps them into methods that you can call with a single line of code.

jQuery also simplifies a lot of the complicated things from JavaScript, like AJAX calls and DOM manipulation.

The jQuery library contains the following features:

HTML/DOM manipulation
CSS manipulation
HTML event methods
Effects and animations
AJAX
Utilities

What You Should Already Know

Before you start studying jQuery, you should have a basic knowledge of:

HTML
CSS
JavaScript

What is jQuery?

jQuery is a lightweight, "write less, do more", JavaScript library.

The purpose of jQuery is to make it much easier to use JavaScript on your website.

jQuery takes a lot of common tasks that require many lines of JavaScript code to accomplish, and wraps them into methods that you can call with a single line of code.

jQuery also simplifies a lot of the complicated things from JavaScript, like AJAX calls and DOM manipulation.

The jQuery library contains the following features:

HTML/DOM manipulation
CSS manipulation
HTML event methods
Effects and animations
AJAX
Utilities

What is PHP?

A web server programming language

PHP is an acronym for "PHP: Hypertext Preprocessor"
PHP is a widely-used, open source scripting language
PHP scripts are executed on the server
PHP is free to download and use

What is PHP?

PHP is an acronym for "PHP: Hypertext Preprocessor"
PHP is a widely-used, open source scripting language
PHP scripts are executed on the server
PHP is free to download and use.

What is a PHP File?

PHP files can contain text, HTML, CSS, JavaScript, and PHP code
PHP code are executed on the server, and the result is returned to the browser as plain HTML
PHP files have extension ".php".

What Can PHP Do?

PHP can generate dynamic page content
PHP can create, open, read, write, delete, and close files on the server
PHP can collect form data
PHP can send and receive cookies
PHP can add, delete, modify data in your database
PHP can be used to control user-access
PHP can encrypt data.

What is JavaScript?

The language for programming web pages

JavaScript is the programming language of HTML and the Web.

Programming makes computers do what you want them to do.

JavaScript is easy to learn.

Why Study JavaScript?

JavaScript is one of the 3 languages all web developers must learn:

1. HTML to define the content of web pages

2. CSS to specify the layout of web pages

3. JavaScript to program the behavior of web pages

This tutorial is about JavaScript, and how JavaScript works with HTML and CSS.

Learning Speed

In this tutorial, the learning speed is your choice.

Everything is up to you.

If you are struggling, take a break, or reread the material.

Always make sure you understand the "Try-it-Yourself" examples and exercises.

Did You Know?

JavaScript and Java are completely different languages, both in concept and design.
JavaScript was invented by Brendan Eich in 1995, and became an ECMA standard in 1997.
ECMA-262 is the official name. ECMAScript 6 (released in June 2015) is the latest official version of JavaScript.

What is CSS?

The language for styling web pages

;- CSS stands for Cascading Style Sheets
CSS describes how HTML elements are to be displayed on screen, paper, or in other media
CSS saves a lot of work. It can control the layout of multiple web pages all at once
External stylesheets are stored in CSS files

CSS is a stylesheet language that describes the presentation of an HTML (or XML) document.

CSS describes how elements must be rendered on screen, on paper, or in other media.

This tutorial will teach you CSS from basic to advanced.

What is HTML?

The language for building web pages

:- HTML is a markup language for describing web documents (web pages).

HTML stands for Hyper Text Markup Language
A markup language is a set of markup tags
HTML documents are described by HTML tags
Each HTML tag describes different document content

HTML-Hyper Text Markup Language.

HTML is a markup language for describing web documents (web pages).

HTML stands for Hyper Text Markup Language
A markup language is a set of markup tags
HTML documents are described by HTML tags
Each HTML tag describes different document content

HyperText Markup Language, commonly referred to as HTML, is the standard markup language used to create web pages. Along with CSS, and JavaScript, HTML is a cornerstone technology, used by most websites to create visually engaging webpages, user interfaces for web applications, and user interfaces for many mobile applications.Web browsers can read HTML files and render them into visible or audible web pages. HTML describes the structure of a website semantically along with cues for presentation, making it a markup language, rather than a programming language.

HTML elements form the building blocks of all websites. HTML allows images and objects to be embedded and can be used to create interactive forms. It provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items.

The language is written in the form of HTML elements consisting of tags enclosed in angle brackets (like <html>). Browsers do not display the HTML tags and scripts, but use them to interpret the content of the page.

HTML can embed scripts written in languages such as JavaScript which affect the behavior of HTML web pages. Web browsers can also refer to Cascading Style Sheets (CSS) to define the look and layout of text and other material. The World Wide Web Consortium (W3C), maintainer of both the HTML and the CSS standards, has encouraged the use of CSS over explicit presentational HTML since 1997