Regex guru needed! Looking for filenames

[twoeyes]

SHORT AND SWEET VERSION:
I need to get a regular expression that will find any filenames in a document with the extension ".esp" and will work with PHP.

LONG WINDED VERSION:
I'm currently trying to develop a PHP friendly regex expression to search a document and find all files of a specific extension... The file names are surrounded by non ASCII characters which might be why i'm having this problem.

Basically i need to do one of two things (or both!):

1. Remove all non ASCII characters from the document
2. Just pick out the file names while ignoring the non-ASCII characters

Here is a function i've found to work when testing on an online regex tester:

[0-9a-zA-Z-'_. ]*\.esp

This does not, however work when putting it into my script. I eaither get an error with preg_replace about the (or . or even +), or I get NO error but no results with ereg(). wonders if i need a special library or something*

Anyway if you guys could help that would be great.

[Drakla]

Show the appropriate chunk of your code. I'd be using preg_match_all, probably as ereg is cack.