What are potential pitfalls when transferring variables between PHP files?

When transferring variables between PHP files, potential pitfalls include variable scope issues, data type inconsistencies, and security vulnerabilities if user input is not properly sanitized. To avoid these pitfalls, it is recommended to use sessions or cookies to pass variables securely between PHP files. 

// Sending variable from one PHP file to another using sessions
// File 1: sending_file.php
session_start();
$_SESSION['variable_name'] = $variable_value;

// File 2: receiving_file.php
session_start();
$received_variable = $_SESSION['variable_name'];

Keywords

variable scope include require global keyword data leakage

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