a=ASHUS<br>
b=ASHUS     (Second one with white space on left side)

if ($qOpt1a==$qOpt2a or $qOpt1a==$qOpt3a or $qOpt1a==$qOpt4a or $qOpt2a==$qOpt3a or $qOpt2a==$qOpt4a or $qOpt4a==$qOpt3a)
{ echo "<script>
            alert('Option should not be same');
      </script>";}

if (ltrim($str1) === ltrim($str2)) {
    // strings are the same, ignoring leading white space
}