How can i run multiple queries on my code in php?

I have tried this code, but i'm getting errors

$sql[0] = "INSERT INTO classtb
                    (classname, duration, classdate, cost, location, 
                    instructor, client, subclient, courseware, note)  
            VALUES('$classname', '$duration', '$classdate', '$cost', 
                    '$loc2name', '$instructor','$client','$subclient', 
                    '$courseware', '$note')";
$sql[1] = "INSERT INTO locationtb(slocation, address, note)  
            VALUES('$loc2name', '$loc2address', '$loc2note')";
//etc...

foreach ($sql as $x) {
    if ($db->query($sql[$x])) {
         echo "worked";
    else{
         echo "Didn't work";
    }
}

I'm getting double error as both are not loading into the tables