The *config.m4* file adds any extension-specific configuration options. If your extension relies on external libraries and header files, you need to define those in this file and uncomment the *--with-xmms* section. If your extension does not rely on any external libraries, uncomment the *--enable-xmms* section. The *ext_skel* script created a sample *xmms.php* script. A quick way to check if your extension is working is to edit this script and add *dl('xmms.so')* to the top. Then run it through your command-line PHP parser: