Where can one find reliable documentation on updating PHP code for compatibility with version 5 and above?

To update PHP code for compatibility with version 5 and above, it is essential to review the PHP manual and documentation for deprecated features and changes in syntax. Additionally, utilizing tools like PHP Compatibility Checker can help identify specific issues that need to be addressed. Updating code to use modern PHP features and functions will ensure compatibility with newer versions of PHP.

// Example of updating code to use newer PHP syntax
// Before:
$old_array = array(1, 2, 3);
// After:
$new_array = [1, 2, 3];