With a few adaptations it can be used to make an online mp3join app. Originally crafted for personal project.
This project combines other open projects such as mp3file.php, phpmp3.php and jquery.bsmselect.js. Check
their licenses if you have any doubt.
Put some mp3 files in the input folder. Then use the officium2mp3.php file to join these mp3 in the
chosen order. Output (final mp3 file) will appear in the output folder.
Note/Limitation: Final mp3 will have corrupted mp3 id-tag.