php - mysqli_num_rows() alwayes return 0 even the user is right -

this login page. returns 0 user , pass right

session_start(); $conn = mysqli_connect('localhost','root','','script');  if (isset($_post['sub'])) {     $user = $_post['user'];     $pass = $_post['pass'];      $result = mysqli_query($conn,'select * admin username = "$user" , password = "$pass"');     echo mysqli_num_rows($result);  }    ?> 

`

this code should work:

session_start(); $conn = mysqli_connect('localhost','root','','script');  if (isset($_post['sub'])) {    $user = $_post['user'];   $pass = $_post['pass'];   $result = mysqli_query($conn,"select * admin username = '$user' , password = '$pass'");  echo mysqli_num_rows($result);  }   ?> 

just change quotes.