flawless script

hi guys, how does everyone usually go about posting within a script ? i usually contain everything i need to do for a script within the same script without the need for a seperate file for posting like so switch ($_POST['action']) { case 'insert': insert into db break; case 'edit': edit content break; } to keep the files to a minimum is this cool ? should i especially check for $_POST when inserting to make it more robust ? or someone could go action=insert without actually posting first