| Macro | Description | 
| AC_MSG_CHECKING(message) | Prints a "checking <message>" text
         during configure. | 
| AC_MSG_RESULT(value) | Gives the result to AC_MSG_CHECKING;
         should specify either yes or no as value. | 
| AC_MSG_ERROR(message) | Prints message as error message
         during configure and aborts the script. | 
| AC_DEFINE(name,value,description) | Adds
         #define to php_config.h with the value of
         value and a comment that says description (this
         is useful for conditional compilation of your module). | 
| AC_ADD_INCLUDE(path) | Adds a compiler include path; for example, used  if the
         module needs to add search paths for header files. | 
| AC_ADD_LIBRARY_WITH_PATH(libraryname,librarypath) | Specifies an additional library to link. | 
| AC_ARG_WITH(modulename,description,unconditionaltest,conditionaltest) | Quite a powerful macro, adding the
         module with description to the
         configure --help output. PHP checks
         whether the option
         --with-<modulename> is given to the
         configure script. If so, it runs the
         script unconditionaltest (for example,
         --with-myext=yes), in which case the value
         of the option is contained in the variable
         $withval. Otherwise, it executes
         conditionaltest. | 
| PHP_EXTENSION(modulename,
          [shared]) | This macro is a must to call for PHP
         to configure your extension. You can supply a second argument
         in addition to your module name, indicating whether you intend compilation as a
         shared module. This will result in a definition at compile time for your
         source as COMPILE_DL_<modulename>. |