PHP用户名和密码验证使用password_verify

我目前正在尝试更新我不安全的登录系统。但是不能弄清楚如何合并一个if (password_verify..)命令。

任何帮助都将是非常感激的。

//Create query
$qry="SELECT * FROM user WHERE username='$username' AND password='$password'";
$result=mysql_query($qry);
if($result) {
    if(mysql_num_rows($result) > 0) {
    //IF Login Successful
        session_regenerate_id();
        $user = mysql_fetch_assoc($result);
        $_SESSION['SESS_USER_ID'] = $user['user_id'];
        $_SESSION['SESS_FIRST_NAME'] = $user['username'];
        $_SESSION['SESS_LAST_NAME'] = $user['password'];
        session_write_close();
        header("location: home.php");
        exit();
    }else {
        //IF Login failed
        $errmsg_arr[] = 'user name and password not found';
        $errflag = true;
        if($errflag) {
            $_SESSION['ERRMSG_ARR'] = $errmsg_arr;
            session_write_close();
            header("location: index.php");
            exit();
        }
    }