php mysql update non-existent record

Question

I use this piece of php to insert/update mysql db. Please see my question in the comment part at corresponding lines. Thanks.

        //Connecting to your database
        mysql_connect($hostname, $username, $password) OR DIE ("Unable to connect to database! Please try again later.");
        mysql_select_db($dbname);

        arr = array();
        if (strcasecmp($actionIn, 'insert') == 0) {
           $query = "INSERT INTO $usertable (id, fname, lname) VALUES ('$id', '$fname', 'lname'";
           $result = mysql_query($query) or die(mysql_error()); //AT THIS STEP, I would get error message if I insert a duplicated id into table, no following json_encode would not print out, that's what I want.
           if ($result) {
              $arr['inserted'] = 'true';
           }
           exit(json_encode($arr));
        }

        if (strcasecmp($actionIn, 'update') == 0) {
           $query = "UPDATE $usertable SET id = '$id', fname = '$fname', lname = '$lname' WHERE id = '$id'";
           $result = mysql_query($query) or die(mysql_error()); //AT THIS STEP, if I update a non-existent id, I don't get error, and the following steps continue to execute. I want the error info or return me a false.
           if ($result) {
              $arr['updated'] = 'true';
           }
       exit(json_encode($arr));
        }

I also tried these, but both num_rows and affected_rows return 0. why?

       $row_cnt = $result->num_rows;
           printf("Result set has %d rows.\n", $row_cnt);
       $aff_cnt = $result->affected_rows;
       printf("Result set aff %d rows.\n", $aff_cnt);

Thanks for your help!

Answer 1

If UPDATE doesn't match anything to update it will simply return. This is not an error. To find out whether it's updated anything use mysql_affected_rows().

Note: mysql_*() doesn't support the OOP form, so you should use mysql_affected_rows(), which should work for your second case above.

This will give you:

if (strcasecmp($actionIn, 'update') == 0) {
       $query = "UPDATE $usertable SET id = '$id', fname = '$fname', lname = '$lname' WHERE id = '$id'";
       $result = mysql_query($query) or die(mysql_error()); 
       if (mysql_affected_rows() !== 0) {
          $arr['updated'] = 'true';
       }

Side note: mysql_*() is deprecated and will be removed. You should use mysqli or PDO for new code.