What are the differences between "audio/x-mpeg" and "audio/mpeg" file types in PHP?

The main difference between "audio/x-mpeg" and "audio/mpeg" file types in PHP is that "audio/x-mpeg" is an unofficial MIME type while "audio/mpeg" is the official MIME type for MPEG audio files. To ensure better compatibility and adherence to standards, it is recommended to use "audio/mpeg" over "audio/x-mpeg" when working with MPEG audio files in PHP.

// Set the correct MIME type for MPEG audio files
header('Content-Type: audio/mpeg');