警告：mysqli_num_rows（）期望參數1爲mysqli_result，在38行中的/opt/lampp/htdocs/internshala/controller/signup.php中給出的數組

Question

可捕獲的致命錯誤：類mysqli_result的對象無法轉換爲字符串in /opt/lampp/htdocs/internshala/controller/signup.php第40行

   if(isset($_POST['btn-login'])) 
       { 
        $username = trim($_POST['username']); 
        $username = strip_tags($username); 
        $username = htmlspecialchars($username); 
        $qry="select id,pwd,username from users where username='".$_POST['username']."'"; 
        $res=mysqli_query($conn,$qry); 
        $row=mysqli_fetch_array($res); 
        $count = mysqli_num_rows($row); // if uname/pass correct it returns must be 1 row 
        //echo $_POST['pwd']; 
        echo $res; 
        echo $count; 
        echo $row; 
        if($count == 1 && $row['pwd']==$_POST['pwd']) { 
        echo "djfgk"; 
        $_SESSION['username'] = $row['username']; 
        $_SESSION['userid']=$row['id']; 
        header("Location: userdashboard.php"); 
        } else { 
        $errMSG = "Incorrect Credentials, Try again..."; 
        echo $errMSG; 
        } 
       } 

Answer 1

由於錯誤提示參數應該是mysqli_result對象。因此請使用mysqli_query()的返回值

$res=mysqli_query($conn,$qry); 

$count = mysqli_num_rows($res); 
//      ^^^^ 
$row=mysqli_fetch_array($res); 

Answer 2

這就是問題所在

$count = mysqli_num_rows($row); 

這應該是

$count = mysqli_num_rows($res);