php global variables

php global variables

Several predefined variables in PHP are "superglobals", which means that they are always accessible, regardless of scope - and you can access them from any function, class or file without having to do anything special.

The PHP superglobal variables are:

$GLOBALS
$_SERVER
$_REQUEST
$_POST
$_GET
$_FILES
$_ENV
$_COOKIE
$_SESSION

php globals

$GLOBALS is a PHP super global variable which is used to access global variables from anywhere in the PHP script (also from within functions or methods).

PHP stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable.

The example below shows how to use the super global variable $GLOBALS:

<?php 
$x = 75; 
$y = 25;

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

addition(); 
echo $z; 
?>

php server

$_SERVER is a PHP super global variable which holds information about headers, paths, and script locations.

The example below shows how to use some of the elements in $_SERVER:

<?php 
echo $_SERVER['PHP_SELF'];
echo "<br>";
echo $_SERVER['SERVER_NAME'];
echo "<br>";
echo $_SERVER['HTTP_HOST'];
echo "<br>";
echo $_SERVER['HTTP_REFERER'];
echo "<br>";
echo $_SERVER['HTTP_USER_AGENT'];
echo "<br>";
echo $_SERVER['SCRIPT_NAME'];
?>

sort array

array sort functions

In this chapter, we will go through the following PHP array sort functions:

sort() - sort arrays in ascending order
rsort() - sort arrays in descending order
asort() - sort associative arrays in ascending order, according to the value
ksort() - sort associative arrays in ascending order, according to the key
arsort() - sort associative arrays in descending order, according to the value
krsort() - sort associative arrays in descending order, according to the key
sort array in ascending order

The following example sorts the elements of the $cars array in ascending alphabetical order:

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

The following example sorts the elements of the $numbers array in ascending numerical order:

Example
<?php
$numbers = array(4, 6, 2, 22, 11);
sort($numbers);
?>

sort array descending

The following example sorts the elements of the $cars array in descending alphabetical order:

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

The following example sorts the elements of the $numbers array in descending numerical order:

Example
<?php
$numbers = array(4, 6, 2, 22, 11);
rsort($numbers);
?>

Array in php

what is array

An array is a special variable, which can hold more than one value at a time.

If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:

$cars1 = "Volvo";
$cars2 = "BMW";
$cars3 = "Toyota";
However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?

The solution is to create an array!

An array can hold many values under a single name, and you can access the values by referring to an index number.

In PHP, the array() function is used to create an array:

array();
In PHP, there are three types of arrays:

Indexed arrays - Arrays with a numeric index
Associative arrays - Arrays with named keys
Multidimensional arrays - Arrays containing one or more arrays

In PHP, the array() function is used to create an array:

array();
In PHP, there are three types of arrays:

Indexed arrays - Arrays with a numeric index
Associative arrays - Arrays with named keys
Multidimensional arrays - Arrays containing one or more arrays

indexed array

There are two ways to create indexed arrays:

The index can be assigned automatically (index always starts at 0), like this:

$cars = array("Volvo", "BMW", "Toyota");
or the index can be assigned manually:

$cars[0] = "Volvo";
$cars[1] = "BMW";
$cars[2] = "Toyota";
The following example creates an indexed array named $cars, assigns three elements to it, and then prints a text containing the array values:

<?php
$cars = array("Volvo", "BMW", "Toyota");
echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>

The count() function is used to return the length (the number of elements) of an array:

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

indexed array

To loop through and print all the values of an indexed array, you could use a for loop, like this:

<?php
$cars = array("Volvo", "BMW", "Toyota");
$arrlength = count($cars);

for($x = 0; $x < $arrlength; $x++) {
echo $cars[$x];
echo "<br>";
}
?>

php associative array
Associative arrays are arrays that use named keys that you assign to them.

There are two ways to create an associative array: 

$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
or:

$age['Peter'] = "35";
$age['Ben'] = "37";
$age['Joe'] = "43";
The named keys can then be used in a script:

<?php
$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
echo "Peter is " . $age['Peter'] . " years old.";
?>

php function with example

php functions with example
A user defined function declaration starts with the word "function":

Syntax
function functionName() {
code to be executed;
}
Note: A function name can start with a letter or underscore (not a number).

Tip: Give the function a name that reflects what the function does!

Note Function names are NOT case-sensitive.
In the example below, we create a function named "writeMsg()". The opening curly brace ( { ) indicates the beginning of the function code and the closing curly brace ( } ) indicates the end of the function. The function outputs "Hello world!". To call the function, just write its name:

<?php
function writeMsg() {
echo "Hello world!";
}

writeMsg(); // call the function
?>

Information can be passed to functions through arguments. An argument is just like a variable.

Arguments are specified after the function name, inside the parentheses. You can add as many arguments as you want, just separate them with a comma.

The following example has a function with one argument ($fname). When the familyName() function is called, we also pass along a name (e.g. Jani), and the name is used inside the function, which outputs several different first names, but an equal last name:

<?php
function familyName($fname) {
echo "$fname Refsnes.<br>";
}

familyName("Janis");
familyName("Hedge");
familyName("Stadle");
familyName("Kait Jim");
familyName("Borgde");
?>

The following example has a function with two arguments ($fname and $year):

Example
<?php
function familyName($fname, $year) {
echo "$fname Refsnes. Born in $year <br>";
}

familyName("Hege", "1975");
familyName("Stale", "1978");
familyName("Kai Jim", "1983");
?>

php function with argumemts

The following example shows how to use a default parameter. If we call the function setHeight() without arguments it takes the default value as argument:

<?php
function setHeight($minheight = 50) {
echo "The height is : $minheight <br>";
}

setHeight(350);
setHeight(); // will use the default value of 50
setHeight(135);
setHeight(80);
?>

php function with return

<?php
function sum($x, $y) {
$z = $x + $y;
return $z;
}

echo "5 + 10 = " . sum(5, 10) . "<br>";
echo "7 + 13 = " . sum(7, 13) . "<br>";
echo "2 + 4 = " . sum(2, 4);
?>

For loop with example

for loop with example

The for loop is used when you know in advance how many times the script should run.

Syntax
for (init counter; test counter; increment counter) {
code to be executed;
}
Parameters:

init counter: Initialize the loop counter value
test counter: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.
increment counter: Increases the loop counter value
The example below displays the numbers from 0 to 10:

<?php 
for ($x = 0; $x <= 10; $x++) {
echo "The number is: $x <br>";
} 
?>

Syntax
foreach ($array as $value) {
code to be executed;
}

<?php 
$colors = array("w3schoolworld", "green", "blue", "yellow"); 

foreach ($colors as $value) {
echo "$value <br>";
}
?>

php loops with example

php loops with example

In PHP, we have the following looping statements:

while - loops through a block of code as long as the specified condition is true
do...while - loops through a block of code once, and then repeats the loop as long as the specified condition is true
for - loops through a block of code a specified number of times
foreach - loops through a block of code for each element in an array

Syntax
while (condition is true) {
code to be executed;
}

<?php 
$x = 1; 

while($x <= 5) {
echo "The number is: $x <br>";
$x++;
} 
?>

Syntax
do {
code to be executed;
} while (condition is true);

<?php 
$x = 1; 

do {
echo "The number is: $x <br>";
$x++;
} while ($x <= 5);
?>

Notice that in a do while loop the condition is tested AFTER executing the statements within the loop. This means that the do while loop would execute its statements at least once, even if the condition is false the first time.

The example below sets the $x variable to 6, then it runs the loop, and then the condition is checked:

Example
<?php 
$x = 6;

do {
echo "The number is: $x <br>";
$x++;
} while ($x<=5);
?>

php if else statement with example

Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this.

In PHP we have the following conditional statements:

if statement - executes some code only if a specified condition is true
if...else statement - executes some code if a condition is true and another code if the condition is false
if...elseif....else statement - specifies a new condition to test, if the first condition is false
switch statement - selects one of many blocks of code to be executed
PHP - The if Statement
The if statement is used to execute some code only if a specified condition is true.

Syntax
if (condition) {
code to be executed if condition is true;
}
The example below will output "Have a good day!" if the current time (HOUR) is less than 20:

<?php
$t = date("H");

if ($t < "20") {
echo "Have a good day!";
}
?>

Syntax
if (condition) {
code to be executed if condition is true;
} else {
code to be executed if condition is false;
}
The example below will output "Have a good day!" if the current time is less than 20, and "Have a good night!" otherwise:

<?php
$t = date("H");

if ($t < "20") {
echo "Have a good day!";
} else {
echo "Have a good night!";
}
?>

Syntax
if (condition) {
code to be executed if condition is true;
} elseif (condition) {
code to be executed if condition is true;
} else {
code to be executed if condition is false;
}

<?php
$t = date("H");

if ($t < "10") {
echo "Have a good morning!";
} elseif ($t < "20") {
echo "Have a good day!";
} else {
echo "Have a good night!";
}
?>

php switch statement

php switch statement

Syntax
switch (n) {
case label1:
code to be executed if n=label1;
break;
case label2:
code to be executed if n=label2;
break;
case label3:
code to be executed if n=label3;
break;
...
default:
code to be executed if n is different from all labels;
}

<?php
$fcolor = "red";

switch ($fcolor) {
case "red":
echo "Your favorite color is red!";
break;
case "blue":
echo "Your favorite color is blue!";
break;
case "green":
echo "Your favorite color is green!";
break;
default:
echo "Your favorite color is neither red, blue, nor green!";
}
?>

PHP operators

Operators are used to perform operations on variables and values.

PHP divides the operators in the following groups:

Arithmetic operators
Assignment operators
Comparison operators
Increment/Decrement operators
Logical operators
String operators
Array operators