What are common issues when running PHP code online versus locally?

One common issue when running PHP code online versus locally is the difference in server configurations. This can lead to compatibility issues with certain functions or extensions that work locally but not on the online server. To solve this, it is important to ensure that the online server has the necessary PHP extensions and settings enabled.

// Check if a specific PHP extension is enabled
if (!extension_loaded('pdo_mysql')) {
    die('The pdo_mysql extension is not enabled on this server.');
}