准备语句行数

Question

我已经创建了一个名为SQL的类，在类的内部我有一个名为Login（）的函数。我设法通过以下方式使其工作：

if (isset($_POST['username']) && isset($_POST['password'])) {
    $con = $this->DbConnect();
    $password = $_POST['password'];
    $username = strtolower($_POST['username']);
    $password_hash = sha1($password);
    $sql = "SELECT * FROM users WHERE email='$username' and password='$password_hash' LIMIT 1";
    $query = mysqli_query($con, $sql);
    $count = mysqli_num_rows($query);
    //Login succes
    if ($count == 1) {
        echo "succes";
    }
}

我已经通过以下方式尝试了它并且无法使其工作，你们有任何想法为什么？

更新

 $con = $this->DbConnect();
            $password = $_POST['password'];
            $username = strtolower($_POST['username']);
            $password_hash = password_hash($password, PASSWORD_DEFAULT);
            $stmt = $this->DbConnect()->prepare("SELECT email,password FROM users WHERE email=? and password=? LIMIT 1");
            $stmt->bind_param("ss", $username, $password_hash);
            $stmt->execute();
            $stmt->store_result();
            $stmt->bind_result($username, $password_hash);
            $stmt->fetch();
            $count = $stmt->num_rows;
            var_dump($password_hash);
            echo $count;
            //Login succes
            if (password_verify($password, $password_hash)){
            }

            if ($count == 1){
//                header("location:");


            }else{
//                header("location:?error=1");
            }