I'll make this as short and sweet as possible...
Your first friend:
PHP's ereg functions. http://www.php.net/ereg to start reading about them.
Your second friend:
A nifty little SQL trick called "LIKE": "SELECT * FROM table WHERE field LIKE '%".$search_text."%' ORDER BY date DESC"
These are your friends. Use them, as that is what they desire for you to do. 😉