PHP: Superglobal Variables
One of the things that makes PHP very easy to use in a web environment are the super global variables that are available to every PHP script at any time during execution. The super globals available are:
These super globals can be accessed at any time to gain valuable information, such as the URL of the website where your script is executing (i.e., $_SERVER['SERVER_NAME']), cookies, a session object, or form data from a Post or Get call.
You can see what any of the variables has in it by typing the following code (changing the global variable name) into a test page on your website:
<?php print_r($_SERVER); ?>
This will print out all of the key/value pairs that the specified global array variable holds. To access an individual key/value pair in the variable, try this:
<?php echo($_SERVER['PHP_SELF']); ?>
Some of the most-used global variables are:
$GLOBALS: If you want at any time to see what global variables are available, print out this $GLOBALS variable. It holds all the super global variables in it, along with any global variables you create. We will discuss creating your own global variables in a later lesson.
$_SERVER: At any time, the $_SERVER variable is available to give you information about the server your scripts are running on.
$_POST: On submission of an HTML form, whichever file you choose to process the form has access to the $_POST variable, which contains all the elements and values of the form.
$_SESSION: You can store session information for each user in this variable. We will discuss how to use session information in a later lesson.