Check for an existing value = $input

[Anonymous]

You're missing one line of code. The $res value you're getting is just a reference link to the actual results, not the result itself! Try this:

$result = mysql_query("SELECT RTA FROM maindcp WHERE RTA = '$rga' limit 1");
if (@mysql_fetch_rows($result)) {
list($res) = mysql_fetch_row($result);
//$res is now equal to what you want
} else {
print "\$res doesn't exist";
}