PHP Predefined Variables

PHP has many predefined variables to use in all scripts, these variables represent everything.

PHP Superglobals
PHP superglobals are built-in variables that are always available in all scopes. 

There are several predefined superglobal variables listed here :

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

 

$GLOBALS
PHP $GLOBALS variable reference or changed all variables into the global scope.

Example :

<?php

    $var = "hello";

    function Test() {
	
        $var2 = "program";
	
        $GLOBALS['var3'] = "good bye";   // Changed local scope to global scope
	
        echo $GLOBALS['var'] . " " . $var2;   // used outside variable inside function without argument with global scope
        echo "<br/>";
	
    }

    Test();

    echo $var3;
	
?>

Output :

 

$_SERVER
PHP $_SERVER is an array that contains information such as Headers, Path & Script locations, etc. 

$_SERVER works with HTTP.

Example :

<?php

    $array = $_SERVER;

    foreach( $array as $key => $value ) {
	
        echo $key . " => " . $value ."<br/>";
	
    }
	
?>

 

$_GET
PHP $_GET accepts HTTP request to get data.

Such as a URL given as 'http://www.example.com/?var=john' that contains HTTP GET request.

Example :

<?php

    $data = $_GET['var'];   // This request get from URL /?var=john
	
    echo $data;
	
?>

Output :

 

$_POST
PHP $_POST accepts HTTP request to post data. $_POST also used to post HTML form data after submission. 

Such as an HTML form given here, After submitting data It will be posted via HTTP $_POST variable.

 

Example :

<?php

    $var1 = $_POST['fname'];
	
    $var2 = $_POST['lname'];
	
    echo $var1 . " " . $var2;
	
?>

Output :

 

$_REQUEST
PHP $_REQUEST accepts HTTP both request to Get and Post data. 

$_REQUEST also accepts HTTP $_COOKIE requests.

Example :

<?php

    // Understand from previous $_GET & $_POST example

    $data = $_REQUEST['var'];
	
    echo $data;
	
    echo "<br/>"
	
    $var1 = $_REQUEST['fname'];
	
    $var2 = $_REQUEST['lname'];
	
    echo $var1 . " " . $var2;
	
?>

 Output :