PHP Source Code Help

I am trying to debug my custom TCP stack which is running under Linux OS. Do to some bug in my stack or missing feature I am getting error following from php. failed to open stream Which I have traced to file: php-4.4.7/main/streams.c and function: _php_stream_open_wrapper_ex

       stream = wrapper->wops->stream_opener(wrapper, path_to_open, mode, options ^ REPORT_ERRORS,
                opened_path, context STREAMS_REL_CC TSRMLS_CC);

Error condition occurs when stream is assigned NULL from wrapper->wops->stream_opener call (see above line). I need some help figuring out which function is call by pointer wrapper->wops->stream_opener. I tried putting debug statements in some functions which are called on pointers (based on different ops (read / write / flush operations, etc.), so far I have not hit a function pointed by wrapper->wops->stream_opener. Also, if there is any documentation for understanding php source code. Thanks Usman P.S. I know 4.4.7 is old php, but by system is setup with this version for debugging TCP stack (for some reason)