yeah you have a very clear mistake , man

you were telling the parser to look for a varibale called 'a' in first case and 'b' in second .. etc
while you should tell the parser something like this

:
try this and it should work ,,
when typing $_POST['whatever'] , it means there is a variable passed via form in POST method called 'whatever' .. in your case it's 'find' ..
and you assume a value in every case ..
so I wrote ( case 'a' ) means if the value of $_POST['find'] is the string 'a' , excute this line ..
hope I was clear
