In magento the compiler interface is located at System -> Tools -> Compiler but we couldn’t enable the complier through interface.
This article still has some useful tips for dealing with the compiler via the command line
What the compiler does is makes a copy of of every class in a Magento system and places them in a single folder. The class’s full name is used for the filename to ensure uniqueness
This is done once. Then, when Magento is configured to use the compiler classes, its autoload will look in the compiler folder instead of running its normal autoload routine. This spares PHP the overhead of transversing the file system for all the different include paths.
php -f compiler.php help
and you can get the below output:
state Show Compilation State compile Run Compilation Process clear Disable Compiler include path and Remove compiled files enable Enable Compiler include path disable Disable Compiler include path help This help
Now using above commands (state, compile, clear etc) you can play.
This may take a few minutes, as Magento is traversing your system and pulling out every possible class. If you take a look at the includes/src directory, you’ll see all your classes