how to know if array is empty

php mySQL

I want the script to die if the search came up empty. How do I check for that?

example:

$sql = "SELECT * FROM $table_name WHERE id IN (".implode(",", $id_bus1).") and metro ='$metro' ORDER BY business";
}

$result = mysql_query($sql,$connection) or die("Couldn't execute query: business search");

// THE FOLLOWING IS NOT DOING THE JOB
if ($result = ""){
echo "Could not find any businesses in that metro area";
exit;
}

thanks

if (mysql_num_rows($result) <= 0) {
.....

will do the trick

thanks