This function is used to set the Session Module at site or script level.The global configuration can be done in php.ini under the [Session] section and with the name of "session.save_handler". The sessions are saved in files by default, like so:session.save_handler = filesBut with this configuration you set one of your websites to use some other session module (if you have them installed and extension loaded with PHP), like so:<?php// NOTE: You must use this function before starting session with session_start(); to make it work properlysession_module_name('memcache'); // or pgsql or redis etc// You'll need to define a save path also, if the module is other than files, like so:session_save_path('localhost:11211'); // memcache uses port 11211// or you can use multiple for load balancing:session_save_path('localhost:11211:41,otherhost:11211:60') // First part is hostname or path to socket, next is port and the last is the weight for that server//The function also returns the value of the current session module.echo session_module_name(); // will print memcache in our case// or maybe a checkif(session_module_name() != 'memcache'){ // Do something, throw an exception maybe}