realcoder,
I am unsure of what exactly you are asking -- however PHP is NOT a good platform for developing a web crawler.
There are many reasons for this, but here are a few:
PHP needs to be compiled into p-code for processing by an interpreter (such as PHP-CLI) .. this is less efficient than compiling an application in a language such as C/C++.
PHP generally has a script timeout, thus your crawler won't be able to run too quickly.
If I do not understand your question, please let me know.