Why is 0 rows returned from sql query?

Question

PHP

I enter the login and password that matches the database

<form method="POST" action="login.php">
<input type="text" name="login" size="15">

$conn = mysqli_connect("localhost","my_user","sMtWzj6WLNFkrQCa","users");
  if ($conn == false){
    print("Ошибка: Невозможно подключиться к MySQL ".mysqli_connect_error());
  }
  mysqli_set_charset($conn, "utf8");
}
  $qu = "SELECT * FROM data WHERE 'login'='". $_POST["login"] ."' AND 'pass'='". $_POST["pass"]."'";
  $zapros =mysqli_query($conn,$qu);
  
  if($result = mysqli_query($conn,$qu)){
    $rowcount=mysqli_num_rows($result);
  	printf("Result set has %d rows.\n",$rowcount);

I get 0 rows in the output, perhaps an error in the SQL query?

Answer 1

This code contains a SQL Injection vulnerability that is easy to exploit. Read about PDO and Prepared Statements and don't embarrass yourself like that anymore.