php update api

<?php
    $host="localhost"; //replace with database hostname
    $username="username"; //replace with database username
    $password="attendance"; //replace with database password
    $db_name="db_name"; //replace with database name
    $con=mysql_connect("$host", "$username", "$password") or die ("cannot connect");
    mysql_select_db("$db_name") or die ("cannot select DB");
    $matric = $_POST['matric'];
    $mac = $_POST['mac'];
    $sql = "update students set `mac` = '$mac' WHERE `matric` = $matric";
    if(mysql_query($sql)){
        echo 'success';
    }
    else{
        echo 'failure';
    }
    mysql_close($con);
?>