I suspect such a thing does not exist given the many different ways in Perl you can code the same line of Perl...I would think trying to make a conversion script would be very difficult and likely be very error prone. Better to just understand what the perl script is doing, and write the same functionality in php.
Or, if you can dissect the perl script into chunks, perhaps you could make php wrapper functions that invoke those chunks via system() or exec()...I don't like the sound of that but if the Perl code is already doing some heavy lifting for you its probably better to leave it as perl and figure out how you can call it from php.
Good luck.
