PHP不会删除mysql行

Everything seems OK, but it won't delete rows. MySQL version is 5.1. Script is:

<?php

$host="localhost";
$username="***";
$password="***";
$db_name="***";

$db = mysql_connect("$host", "$username", "$password")or die("cannot connect"); 
mysql_select_db("$db_name")or die("cannot select DB");

$sql = "DELETE FROM oc_ixml_cat_map WHERE name='***'";
$result=mysql_query($sql,$db) or die(mysql_error());

if ($result) {
    echo "OK";
}
else {
    echo "Not OK";
}

?>

Try to change the string to:

DELETE FROM oc_ixml_cat_map WHERE id=1

Where 1 is an available ID of your table just to see if the command is running or it is connection problem...