What potential pitfalls should PHP developers be aware of when passing variables from one script to another in a web application?

One potential pitfall PHP developers should be aware of when passing variables from one script to another in a web application is the risk of injection attacks if user input is not properly sanitized. To prevent this, developers should always validate and sanitize user input before passing it to another script. Additionally, developers should be cautious of using global variables to pass data between scripts, as this can lead to security vulnerabilities.

// Sanitize user input before passing it to another script
$userInput = $_POST['user_input'];
$sanitizedInput = filter_var($userInput, FILTER_SANITIZE_STRING);

// Pass the sanitized input to another script using sessions
session_start();
$_SESSION['sanitized_input'] = $sanitizedInput;

// Retrieve the sanitized input in the other script
session_start();
$sanitizedInput = $_SESSION['sanitized_input'];