This document discusses using PHP to distribute processing across multiple machines in parallel. It introduces pthreads, which allows creating multi-threaded PHP applications that are thread-safe. Stream sockets are also presented as a way for processes to communicate, such as a scraper process communicating with a client process. An example is given of how to split an XML document into pieces, send each piece to a scraper process using stream sockets, run the scraping in parallel threads, and collect the results.