php preg_match email validation code

<?php
   function checkemail($str) {
         return (!preg_match("/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix", $str)) ? FALSE : TRUE;
   }
   if(!checkemail("[email protected]")){
      echo "Invalid email address.";
   }
   else{
      echo "Valid email address.";
   }
?>