A few notes to succesfully configure PHP5 to load bcompiler.
In case of using Debian/Ubuntu Linux: When installing from the PECL (PEAR) package, make sure you have the php5-dev library installed in your system (apt-get install php5-dev).
Newer versions of Ubuntu may error out while installing bcompiler thru PECL, asking you to reinstall bzip2. This will not fix the installation. Instead, install the libbz2-dev library (apt-get install libbz2-dev) and try installing bcompiler from PECL again.
After installing bcompiler from PECL, don't forget to make sure you load the bcompiler.so library in your PHP configuration for the new bcompiler functions to become available. This is done by adding the following line to the bottom of your php.ini file(s):
If you were to use the bcompiler functions thru your webserver, you need to restart it to reload the php configuration.