php mysql update non-existent record - php

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.