mp3 / mpg authentication

[Anon]

I have put together a nice php based mp3 server that serves mp3's based out of a directory structure. Currently, it will try to serve any file in the tree as an mp3. I am looking for a way to check a file, and determine whether or not it is a valid mpg, mp2, or mp3 file without looking at the file extension. Does anyone know how to do this, or have a script that will make this possible?

Thanks
~Corey O.~

[Anon]

Most files have an identifier string at the beginning of the file.
Open the file, read a few chars (10 or 20 will do) and see what's in it.

Note: this is just about the slowest possible method of finding out which type the file is.
Using the extension is much faster.
Things you don't want to hear: get your extensions sorted out properly.

[Anon]

I was afraid of the speed issue 🙁 . All of my mp3's are have the proper extensions on them, however I wanted to make my software cross platform compatible. Ideally, I would build an option of using either mp3's, or file identifiers to check for valid mp3 files. Thanks for the suggestion.

~Corey O.~