When I run this PHP code I am getting a fatal error.
Code
    <?php
    $user = 'root';
    $password = 'root';
    $db = 'inventory';
    $host = 'localhost';
    $port = 8888;
    $link = mysqli_init();
    $success = mysqli_real_connect(
       $link,
       $host,
       $user,
       $password,
       $db,
       $port
    );
    ?>
    <?php
    $username = $_POST['username'];
    $password = $_POST['password'];
    $sql = mysql_query("SELECT * FROM login WHERE username = '".$_POST['username']."' and password = '".md5($_POST['password'])."'");
    $row = mysql_num_rows($sql);
    if($rom > 0 )
    {
      session_start();
      $_SESSION['username'] = $_POST['username'];
      $_SESSION['password'] = $_POST['password'];
      echo "login done";
    }else {
      echo "fail login ";
    }
The Error
PHP Fatal error: Uncaught Error: Call to undefined function mysql_query() in /Applications/MAMP/htdocs/lprapp/config.php:23 Stack trace:#0 {main} thrown in /Applications/MAMP/htdocs/lprapp/config.php on line 23
Can someone help me with this issue?