What are the common pitfalls or challenges that may arise when updating PHP versions on a server?

One common challenge when updating PHP versions on a server is compatibility issues with existing code that may rely on deprecated features or functions. To solve this, it's important to thoroughly test the codebase on a local environment with the new PHP version before deploying it to the server. 

// Example code snippet for updating deprecated functions
// Replace deprecated function mysql_connect with mysqli_connect
$mysqli = mysqli_connect('localhost', 'username', 'password', 'database');
if (!$mysqli) {
    die('Could not connect: ' . mysqli_error());
}

Keywords

backward compatibility deprecated functions syntax changes server configuration compatibility issues

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