PHP Superglobals

PHP superglobals are built-in global arrays in PHP that provide access to various types of data throughout your application. They are available in all scopes and can be used to access or manipulate data like form inputs, session variables, cookies, and more. Here’s a rundown of the main PHP superglobals with examples:

1. $_GET

   Contains data sent via the URL query string (HTTP GET method).

   // URL: example.com/index.php?name=John&age=25
   echo $_GET['name']; // Outputs: John
   echo $_GET['age'];  // Outputs: 25
   

2. $_POST

   Contains data sent via the HTTP POST method (usually from forms).

   // Assume a form was submitted with a POST request
   echo $_POST['username']; // Outputs the value of the 'username' field
   echo $_POST['password']; // Outputs the value of the 'password' field
   

3. $_REQUEST

   Contains data from both $_GET and $_POST, and also $_COOKIE.

   // Combining GET and POST data
   echo $_REQUEST['name']; // Outputs the 'name' value from GET or POST
   

4. $_SERVER

   Contains information about the server environment and HTTP headers.

   echo $_SERVER['HTTP_USER_AGENT']; // Outputs the user's browser information
   echo $_SERVER['REQUEST_METHOD'];  // Outputs the request method (GET, POST, etc.)
   

5. $_SESSION

   Used to store session variables. Sessions must be started with session_start() before using $_SESSION.

   session_start();
   $_SESSION['username'] = 'JohnDoe';
   echo $_SESSION['username']; // Outputs: JohnDoe
   

6. $_COOKIE

   Contains cookies sent by the client.

   // Set a cookie first
   setcookie('user', 'JohnDoe', time() + 3600); // Expires in 1 hour
   echo $_COOKIE['user']; // Outputs: JohnDoe (if cookie is set)
   

7. $_FILES

   Contains information about files uploaded through a form.

   // Assuming a form with file upload is submitted
   echo $_FILES['file']['name']; // Outputs the name of the uploaded file
   echo $_FILES['file']['size']; // Outputs the size of the uploaded file
   

8. $_ENV

   Contains environment variables.

   echo $_ENV['PATH']; // Outputs the system path environment variable
   

9. $_GLOBALS

   An associative array containing all global variables.

   $a = 10;
   function test() {
       global $a;
       echo $a; // Outputs: 10
   }
   test();
   

These superglobals provide a way to access data across different parts of your PHP application, making it easier to handle form inputs, manage sessions, and interact with the server and environment.