Finds if a multi field contains a certain reference or value. Should be used as a function in condition of ptb_select.
Advanced version of this function is isThereExt.
Find all records belonging to the category, which code is 5 (they may belong to more categories than one, though, since it's a multi field!):
$var = ptb_select($myDatabase, "isThere('5', '%category')");
Find all records belonging to the category "sci-fi" (again, they may belong to more categories than this one):
$var = ptb_select($myDatabase, "isThere('sci-fi', 'category')");