if($row = mysql_fetch_array($result) does not work in php7

Using "if" statement to determine if a user is an admin drawing from mySQL database.

Every place I have looked says that the mysql_fetch_array is deprecated but does not give any alternatives.

$sql = "SELECT * FROM user WHERE user='$username' && 
  password='$password' ";
  $result = $conn->query($sql); 
  if($row = mysql_fetch_array($result))
       {
    $_SESSION['id'] = "".$row['id']."";
    $_SESSION['username'] = "".$row['user']."";     // Username
    $_SESSION['admin'] = "".$row['admin']."";   // Admin
    $_SESSION['seclvl'] = 1;            // Security Level
    }

The code should connect to the database, using a login form to determine if the SESSION user is a site admin and allow them access to certain pages, if they are not an admin it only shows basic pages. The login does not return the expected results.