Memory cleanup for long-running scripts.
gc_enable(); // Enable Garbage Collector
var_dump(gc_enabled()); // true
var_dump(gc_collect_cycles()); // # of elements cleaned up
gc_disable(); // Disable Garbage Collector
More info:
http://php.net/manual/en/features.gc.php
http://es.php.net/manual/en/function.gc-collect-cycles.php
Via: http://talks.php.net/show/pbc11/25