Basically what ini_set() does is, sets the value of the given configuration option. The configuration option will keep this new value during the script’s execution, and will be restored at the script’s ending. It takes 2 parameters, 1 is variable name, and other is value. I have used the ini_set() function mostly to set the memory limit. This function has helped me lot when I have been working with Drupal site migration to production server.