10.4.6 Why do I get an error that looks something like this: "Warning: 0 is not a MySQL result index in <file> on line <x>" or "Warning: Supplied argument is not a valid MySQL result resource in <file> on line <x>?

You are trying to use a result identifier that is 0. The 0 indicates that your query failed for some reason. You need to check for errors after submitting a query and before you attempt to use the returned result identifier. The proper way to do this is with code similar to the following:

$result = mysql_query("SELECT * FROM tables_priv");
if (!$result) {
    echo mysql_error();
    exit;
}

$result = mysql_query("SELECT * FROM tables_priv")
    or die("Bad query: ".mysql_error());