MySQL＆PHP，mysqli_num_rows總是返回0

Question

我有一個問題，我似乎無法用我的註冊腳本來解決。

這裏的腳本：

<?php 

    //MySQLi connection 

    $con = mysqli_connect("-","-","-","users"); 

    if (mysqli_connect_errno()) 

    { 

    echo "MySQLi Connection was not established: " . mysqli_connect_error(); 

    } 

    //Reading the userdata from the registerp.php page 

    $usr = mysqli_real_escape_string($con,$_POST['username']); 

    $email = mysqli_real_escape_string($con,$_POST['email']); 

    $pass_unhashed = mysqli_real_escape_string($con,$_POST['pass']); 

    $pass = password_hash($pass_unhashed, PASSWORD_DEFAULT); 

    //Checking if user exists 

    $check_usr = mysqli_query($con,"SELECT * FROM users WHERE user_name = '$usr'"); 
    if(check_usr === false) 
    { 
     echo(mysqli_error($con)); 
    } 
    else 
    { 
     if (mysqli_num_rows($con,$check_usr)>=1) 
     { 
      echo "This Username already exists"; 
     } 
     else 
     { 
      echo "This Username is available"; 
     echo "  Name: $usr"; 
     } 
    } 
    ?> 

我的問題是，我無法得到驗證工作（這樣他們不能創建兩個帳戶使用相同的名稱）。

mysqli_num_rows總是返回0（「這個用戶名可用」）即使是在我table

而且我的測試用戶（nevondrax），它似乎並沒有給我任何錯誤，要麼..

我做錯了什麼/我能做些什麼來解決它？

Answer 1

mysqli_num_rows（）接受單個參數的結果集（mysqli_query()或mysqli_store_result()或mysqli_use_result()），所以它應該是，

mysqli_num_rows($check_usr); 

參考：http://php.net/manual/en/mysqli-result.num-rows.php