There are several predefined variables in PHP they called “superglobals”, which means global scope you can access anywhere in the PHP code, and you can access them from any function, class or file without having to do anything special.
Superglobals were introduced in PHP 4.1.0, and are built-in variables that are always available in all scopes.
| $GLOBALS | This variable contains a reference to every variable, which is currently available within the global scope of script. |
| $_GET | This variable is an associative array of the variables passed to the current script via the HTTP GET method |
| $_SERVER | This variable is an array containing the information such as headers, paths, script locations, etc. |
| $_FILES | This variable is also an associative array of items uploaded to the current script via the HTTP POST method |
| $_POST | This variable is also an associative array of variables passed to the current script via the HTTP POST method |
| $_COOKIE | This is an associative array of variables passed to the current script via the HTTP cookies |
| $_REQUEST | This is an associative array consisting of the contents of $_GET, $_POST, and $_COOKIE |
| $_PHP_SELF | This is a string containing the PHP script file name in which it is called |
| $php_errormsg | This is a variable containing the text of the last error message that generated by the PHP |
| $_SESSION | This is an associative array containing the session variables available to the current script |
$GLOBALS is a PHP super global variable which is used to access global variables from anywhere in the PHP script including within functions or methods.
PHP stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable.
Here i am using example of the super global variable $GLOBALS:
<?php
$a = 25;
$b = 35;
function addtwonum() {
$GLOBALS['sum'] = $GLOBALS['a'] + $GLOBALS['b'];
}
addtwonum();
echo $sum;
?>
$_SERVER is a PHP super global variable which holds information about headers, paths, and script locations etc.
This example shows how to use of $_SERVER variable:
<?php echo "Your IP Address Is: " . $_SERVER['REMOTE_ADDR'] . "<br>"; echo "The Current Page Name Is: " . $_SERVER['PHP_SELF'] . "<br>"; echo "You Came From A Page Called: " . $_SERVER['HTTP_REFERER'] . "<br>"; ?>
PHP $_REQUEST is used to collect data after submitting an HTML form, $_REQUEST can be collect data of both POST nad GET method of form.
<html>
<body>
<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
Name: <input type="text" name="your_name">
<input type="submit" name="submit" value="Submit">
</form>
<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$yourname = $_REQUEST['your_name'];
if (empty($yourname)) {
echo "Name is empty";
} else {
echo "Your name is : ".$yourname;
}
}
?>
</body>
</html>
The $_SERVER variable has over thirty elements available, most of which are actually useful. The most common elements, assuming your server supports them, are:
| Variable | Description |
|---|---|
| $_SERVER[‘PHP_SELF’] | The filename of the currently executing script, relative to the document root. |
| $_SERVER[‘SERVER_ADDR’] | The IP address of the server under which the current script is executing. |
| $_SERVER[‘SERVER_NAME’] | The name of the server host under which the current script is executing. If the script is running on a virtual host, this will be the value defined for that virtual host. |
| $_SERVER[‘SERVER_SOFTWARE’] | Server identification string, given in the headers when responding to requests. |
| $_SERVER[‘SERVER_PROTOCOL’] | Name and revision of the information protocol via which the page was requested; i.e. ‘HTTP/1.0’; |
| $_SERVER[‘REQUEST_METHOD’] | Which request method was used to access the page; i.e. ‘GET’, ‘HEAD’, ‘POST’, ‘PUT’. |
| $_SERVER[‘REQUEST_TIME’] | The timestamp of the start of the request. Available since PHP 5.1.0. |
| $_SERVER[‘QUERY_STRING’] | The query string, if any, via which the page was accessed. |
| $_SERVER[‘DOCUMENT_ROOT’] | The document root directory under which the current script is executing, as defined in the server’s configuration file. |
| $_SERVER[‘HTTP_CONNECTION’] | Contents of the Connection: header from the current request, if there is one. Example: ‘Keep-Alive’. |
| $_SERVER[‘HTTP_HOST’] | Contents of the Host: header from the current request, if there is one. |
| $_SERVER[‘HTTP_REFERER’] | The address of the page (if any) which referred the user agent to the current page. |
| $_SERVER[‘HTTP_USER_AGENT’] | This is a string denoting the user agent being which is accessing the page. A typical example is: Mozilla/4.5 [en] (X11; U; Linux 2.2.9 i586). |
| $_SERVER[‘HTTPS’] | Set to a non-empty value if the script was queried through the HTTPS protocol. |
| $_SERVER[‘REMOTE_ADDR’] | The IP address from which the user is viewing the current page. |
| $_SERVER[‘REMOTE_HOST’] | The Host name from which the user is viewing the current page. The reverse dns lookup is based off the REMOTE_ADDR of the user. |
| $_SERVER[‘REMOTE_PORT’] | The port being used on the user’s machine to communicate with the web server. |
| $_SERVER[‘SCRIPT_FILENAME’] | The absolute pathname of the currently executing script. |
| $_SERVER[‘SERVER_ADMIN’] | The value given to the SERVER_ADMIN (for Apache) directive in the web server configuration file. |
| $_SERVER[‘SERVER_PORT’] | The port on the server machine being used by the web server for communication. For default setups, this will be ’80’. |
| $_SERVER[‘SERVER_SIGNATURE’] | String containing the server version and virtual host name which are added to server-generated pages, if enabled. |
| $_SERVER[‘PATH_TRANSLATED’] | Filesystem based path to the current script. |
| $_SERVER[‘SCRIPT_NAME’] | Contains the current script’s path. This is useful for pages which need to point to themselves. |
| $_SERVER[‘REQUEST_URI’] | The URI which was given in order to access this page; for instance, ‘/index.html’. |
| $_SERVER[‘PHP_AUTH_DIGEST’] | When running under Apache as module doing Digest HTTP authentication this variable is set to the ‘Authorization’ header sent by the client. |
| $_SERVER[‘PHP_AUTH_USER’] | When running under Apache or IIS (ISAPI on PHP 5) as module doing HTTP authentication this variable is set to the username provided by the user. |
| $_SERVER[‘PHP_AUTH_PW’] | When running under Apache or IIS (ISAPI on PHP 5) as module doing HTTP authentication this variable is set to the password provided by the user. |
| $_SERVER[‘AUTH_TYPE’] | When running under Apache as module doing HTTP authenticated this variable is set to the authentication type. |