Understanding PHP Superglobals and the $_GLOBALS Variable

PHP is a popular server-side scripting language used for web development. It provides a number of superglobals, which are built-in variables that are always accessible in all scopes of a PHP script. One of these superglobals is the $_GLOBALS variable, which contains a reference to all global variables defined in a PHP script.

In this article, we will dive deeper into the $_GLOBALS variable and its uses in PHP programming.

What are PHP Superglobals?

Superglobals in PHP are special variables that are available in all scopes of a PHP script. This means that they can be accessed from any function, class, or file, without having to declare them as global variables.

The following are the superglobals in PHP:

• $_GET: contains data passed to the script via the URL query string.
• $_POST: contains data passed to the script via a form submission.
• $_COOKIE: contains data passed to the script via cookies.
• $_SESSION: contains data stored in a user's session.
• $_REQUEST: contains data passed to the script via the URL query string, form submission, or cookies.
• $_SERVER: contains information about the server and environment.
• $_ENV: contains information about the environment.
• $_GLOBALS: contains a reference to all global variables defined in a PHP script.

What is the $_GLOBALS Variable in PHP?

The $_GLOBALS variable is a superglobal that contains a reference to all global variables defined in a PHP script. This means that, with the $_GLOBALS variable, you can access any global variable from anywhere in your script.

Here's an example of how the $_GLOBALS variable can be used to access a global variable:

<?php

$x = 10;
$y = 20;

function add() {
  global $x, $y;
  return $x + $y;
}

echo add(); // 30

echo $GLOBALS['x']; // 10
echo $GLOBALS['y']; // 20

?>

In this example, the add() function uses the global keyword to access the $x and $y variables. However, instead of using the global keyword, you can also access these variables through the $_GLOBALS variable.

How to Use the $_GLOBALS Variable in PHP

The $_GLOBALS variable is a powerful tool in PHP programming that can be used to access global variables from any part of your script. Here are a few ways to use the $_GLOBALS variable:

Accessing Global Variables

As we saw in the previous example, you can use the $_GLOBALS variable to access any global variable defined in your script. Here's another example:

<?php

$name = "John Doe";

function greeting() {
  global $name;
  echo "Hello, " . $name;
}

greeting(); // Hello, John Doe

echo $GLOBALS['name']; // John Doe

?>

Modifying Global Variables

The $_GLOBALS variable can also be used to modify global variables. This can be useful if you need to make changes to a global variable from within a function or class.

Here's an example:

<?php

$counter = 0;

function increment() {
  global $counter;
  $counter++;
}

increment();
echo $counter; // 1

echo "\n";

$GLOBALS['counter'] = 10;
echo $counter; // 10

?>

In this example, the increment() function increments the value of the $counter variable. However, you can also modify the value of the $counter variable directly through the $_GLOBALS variable.

Pass Variables between Functions and Classes

The $_GLOBALS variable can also be used to pass variables between functions and classes. This can be useful if you need to share data between different parts of your script.

Here's an example:

<?php

$data = array("name" => "John Doe", "age" => 30);

function display_data() {
  global $data;
  print_r($data);
}

class User {
  function show_data() {
    global $data;
    print_r($data);
  }
}

display_data(); // Array ( [name] => John Doe [age] => 30 )

$user = new User();
$user->show_data(); // Array ( [name] => John Doe [age] => 30 )

$GLOBALS['data']['email'] = "[email protected]";

display_data(); // Array ( [name] => John Doe [age] => 30 [email] => [email protected] )
$user->show_data(); // Array ( [name] => John Doe [age] => 30 [email] => [email protected] )

?>

In this example, the display_data() function and the User class both access the $data variable through the $_GLOBALS variable. This allows you to pass the $data variable between the different parts of your script.

Conclusion

The $_GLOBALS variable is a powerful tool in PHP programming that provides access to all global variables defined in a PHP script. Whether you're accessing, modifying, or passing variables between functions and classes, the $_GLOBALS variable is a versatile tool that can help you write better PHP code.