I don't think one exists in PHP, but the Perl implementation looks like it would be trivial to port to PHP. Mostly just changing all the $string =~ stuff to preg_replace.
Thanks Rish3, I figured this was something that might be used enough to be out there in PHP and I wouldn't have to waste time coding it. This might save a little time tho.
Check the comments on php.net soundex page. There are a couple examples where people rewrote it for other algorithms (i.e. Cologne Phonetic). One of them may give you a good base to build on.