How can including a configuration file affect the functionality of PHP sessions?

Including a configuration file can affect the functionality of PHP sessions if the session settings in the configuration file conflict with the settings in the main PHP file. To solve this issue, make sure to set the session configurations consistently across all files that interact with sessions.

// config.php
session_start();
ini_set('session.cookie_lifetime', 3600);
ini_set('session.gc_maxlifetime', 3600);

// index.php
include 'config.php';
// Other PHP code