PHP登录教程错误

Question

我正在网上关注创建php登录脚本的教程。我遇到了以下错误

  

警告：mysqli_fetch_array（）要求参数1为mysqli_result，第27行/Applications/XAMPP/xamppfiles/htdocs/login.php中给出布尔值

     

警告：mysqli_num_rows（）要求参数1为mysqli_result，第32行/Applications/XAMPP/xamppfiles/htdocs/login.php中给出布尔值

我从一开始就尝试过所有事情，但似乎我采取的步骤并没有出现问题，而是使用代码。因为每次我都会在这里结束。如果有人能帮助我解决问题，我会很高兴的。我希望我不会因为提出愚蠢的问题而讨厌。我还不熟悉php，当我和他们一起玩并问问题时，我发现学习新东西很容易。欢呼

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<?php
	session_start();
	include("connection.php"); //Establishing connection with our database
	
	$error = ""; //Variable for storing our errors.
	if(isset($_POST["submit"]))
	{
		if(empty($_POST["username"]) || empty($_POST["password"]))
		{
			$error = "Both fields are required.";
		}else
		{
			// Define $username and $password
			$username=$_POST['username'];
			$password=$_POST['password'];

			// To protect from MySQL injection
			$username = stripslashes($username);
			$password = stripslashes($password);
			$username = mysqli_real_escape_string($db, $username);
			$password = mysqli_real_escape_string($db, $password);
			$password = md5($password);
			
			//Check username and password from database
			$sql="SELECT uid FROM users WHERE username='$username' and password='$password'";
			$result=mysqli_query($db,$sql);
			$row=mysqli_fetch_array($result,MYSQLI_ASSOC);
			
			//If username and password exist in our database then create a session.
			//Otherwise echo error.
			
			if(mysqli_num_rows($result) == 1)
			{
				$_SESSION['username'] = $username; // Initializing Session
				header("location: home.php"); // Redirecting To Other Page
			}else
			{
				$error = "Incorrect username or password.";
			}

		}
	}

?>

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