PHPLIB & Sessions

Here are little pieces of code right now of my source code. What I want is to make sessions so that I don't check for a username/password on everypage. Right now if you goto recipes.php3?action=memberarea&username=aaaaaa&password=bbbbbb it works, but I don't want that big string, i want to work in sessions, but I don't know how PHPLib works! Everytime it goes into a new area, IE, if($action == "search") { $result = mysql_query("SELECT * FROM members where username LIKE '$username'"); $myrow = mysql_fetch_array($result); if($username == $myrow["username"] && $password == $myrow["password"] && $username && $password) { //show search stuff } else { // show login info } } This is after every action, is there a way i can have a session thing? Please answer ASAP, it is for a job! James Smith