I just finished installing the PECL filter extension on my Debian install (AMD64), and by God, it was painful. This process was so brutal with so many ways to screw up.
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Download PCRE – Perl Compatible Regular Expressions from here. Be sure you have g++ installed (not just gcc as I was getting a strange error). Extract, configure, make and make install. If your running AMD64, be sure to compile using the -fPIC flag. See here for information why. Filter will look for the library in /usr/local/, so youll have to setup a link or copy it from /usr/local/lib/ so the PECL install can find it.