unset() and variables in functions

Hello, In an effort to make an intensive search script as efficient as possible, I was wondering: does unset() actually free the memory of that variable, or does it just empty it? after a function returns, user-defined or PHP-defined, are all the local variables in that function freed, or do I need to free them myself? Thanks in advance, Hans -- Hans Anderson -=- me@hansanderson.com | PHP, MySQL, Flash, Audio Free PHP Stuff at http://www.hansanderson.com/php/: All PHP Full Text Search Engine (nothing but PHP required) Time Tracking Software (track your hours for clients) All PHP Simple Crypto (If Blowfish=Pentagon, Crypto=Boy Scouts) PHP Browser Class (Like Perl's LWP)