What best practices should be followed when passing variables between pages in PHP?

When passing variables between pages in PHP, it is recommended to use sessions or query strings to securely transfer data. Sessions are ideal for sensitive information as they are stored on the server-side, while query strings can be used for non-sensitive data. It is important to validate and sanitize the input data to prevent any security vulnerabilities.

// Sending variable using session
session_start();
$_SESSION['variable_name'] = $variable_value;

// Retrieving variable on another page
session_start();
$variable_value = $_SESSION['variable_name'];

// Sending variable using query string
<a href="nextpage.php?variable_name=<?php echo $variable_value; ?>">Next Page</a>

// Retrieving variable on nextpage.php
$variable_value = $_GET['variable_name'];