How can PHP variables be passed between different PHP files?

To pass PHP variables between different PHP files, you can use sessions or cookies. Sessions store data on the server side and can be accessed across multiple pages during a user's visit. Cookies store data on the client side and can also be used to pass variables between pages. Another option is to use include or require statements to include the PHP file containing the variable in the file where you need to access it.

// File 1: setting a session variable
session_start();
$_SESSION['variable_name'] = $variable_value;

// File 2: accessing the session variable
session_start();
$variable_value = $_SESSION['variable_name'];