Question

我一直在制作登录/注册系统。我遇到的唯一问题是如何使用它以便用户无法注册重复的用户名。我环顾四周，看过很多例子，但我的代码没有用。

我想阻止用户在我的网页上注册时使用相同的用户名。任何帮助表示赞赏。

MySQL表：

Create_User:
ID  |  upload_img |   fullname   |  username  |   role   | password    
1   |  <img>      |   Billy      |  billyuser |   User   | test123
2   |  <img>      |   Admin One  |  adminone  |   Admin  | adminonpass

HTML：

<form action="create_user.php" method="post" enctype="multipart/form-data">

       Profile Photo (Optional)<br>
       (Max file size:2MB, file type:jpeg, jpg, png)<br><br>
       <input type="file" name="fileToUpload" id="fileToUpload" required/><br><br>
       Full Name: &nbsp;
       <input type="text" name="fname" id="fname" size="40" maxlength="70" placeholder="Please enter your full name"><br><br>
       Username: &nbsp;
       <input type="text" name="uname" id="uname" size="35" maxlength="62" placeholder="Please enter your username"><br><br>
       Role: &nbsp;
       Customer<input type="radio" name="role" id="role" value="Customer">
       Administrator<input type="radio" name="role" id="role" value="Admin"><br><br>           

         Password: <br>
         <input type="password" name="pword" id="pword" size="35" pattern=".{6,}" placeholder="Password" title="Six or more characters"><br><br>
         <input type="password" name="cfmpword" id="cfmpword" size="35" placeholder="Confirm Password"><br><br>


         <button type="submit" name="signbtn" style="border:none; background:white; padding:0px">
            <img src="button/Sign%20up.png">
         </button><br>
         <a href="signin.html">Back to Sign In</a>

  </form>

腓：

<?php

if (isset($_FILES["fileToUpload"]["name"])) {

      $file=$_FILES["fileToUpload"]["name"];
      $target="uploadfile/" . $file;
      $fname=$_POST['fname'];
      $uname=$_POST['uname'];
      $role=$_POST['role'];
      $pword=$_POST['pword'];

      $conn=mysqli_connect("localhost", "root", "" , "SportFacility");

      $sql_insert = "INSERT into create_user (upload_img, fullname, username, role,  password) 
      values ('$file', '$fname' , '$uname' , '$role' ,  '$pword' )";

      $result=mysqli_query($conn, $sql_insert);

      $allowedType=array("image/jpeg", "image/jpg", "image/png");
      if(in_array ($_FILES["fileToUpload"]["type"] ,$allowedType))
      {
           echo "<script type='text/jscript'>alert('File type is acceptable')</script>";
      }
      else
      {
          echo "<script type='text/jscript'>alert('Invalid file type')</script>";
          exit();
      }
      if($_FILES["fileToUpload"]["size"] < 2000000)
      { 
          echo "<script type='text/jscript'>alert('File size is acceptable')</script>";
      }
      else
      {
          echo "<script type='text/jscript'>alert('File is too large')</script>";
          exit();
      }
      $directoryfile=move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target);

      if($result)
      {
          header("Location: login.html");
      }
      else
      {
          header("Location: register.html");
      }

mysqli_close($conn);

}

 if (isset($_POST['uname']))
      $uname=$_POST['uname'];
      $conn=mysqli_connect("localhost", "root", "" , "SportFacility");
      $sqluser="SELECT username FROM create_user WHERE username='$uname' ";
      $qresult=mysqli_query($conn, $sqluser);
      $count=mysqli_num_rows($qresult);
      if($count)
      {
           echo "Username is already taken";
      }
      else
      { }
 ?>

Answer 1

首先，使用UNIQUE索引或约束来防止数据库中出现重复的用户名。在MySQL中，这是通过以下命令完成的：

ALTER TABLE `tableName` ADD UNIQUE `indexName` ( `columnName` )

这将防止您的数据库处于错误状态（即，具有相同名称的多个用户）。但是你需要在你的PHP代码中主动处理这个问题，以防止用户收到丑陋的MySQL错误消息，你可以通过首先检查是否使用简单的SELECT 1 FROM tableName WHERE column = value来查看用户名来实现这一点。

最后，永远不要使用字符串连接！使用参数化！有人可以通过在HTML表单中输入SQL命令来轻松破解您的网站！

Answer 2

如果您想检查重复的用户名，那么在将用户名插入表格之前，您的第一步是检查重复。

你的php文件

$conn=mysqli_connect("localhost", "root", "" , "SportFacility");

if (isset($_FILES["fileToUpload"]["name"])) {
  if (isset($_POST['uname']))
  $uname=$_POST['uname'];
  $sqluser="SELECT username FROM create_user WHERE username='$uname' ";
  $qresult=mysqli_query($conn, $sqluser);
  $count=mysqli_num_rows($qresult);
  if($count > 0)
  {
       echo "Username is already taken";
  }
  else
  { 

  $file=$_FILES["fileToUpload"]["name"];
  $target="uploadfile/" . $file;
  $fname=$_POST['fname'];
  $uname=$_POST['uname'];
  $role=$_POST['role'];
  $pword=$_POST['pword'];

  $sql_insert = "INSERT into create_user (upload_img, fullname, username, role,  password) 
  values ('$file', '$fname' , '$uname' , '$role' ,  '$pword' )";

  $result=mysqli_query($conn, $sql_insert);

  $allowedType=array("image/jpeg", "image/jpg", "image/png");
  if(in_array ($_FILES["fileToUpload"]["type"] ,$allowedType))
  {
       echo "<script type='text/jscript'>alert('File type is acceptable')</script>";
  }
  else
  {
      echo "<script type='text/jscript'>alert('Invalid file type')</script>";
      exit();
  }
  if($_FILES["fileToUpload"]["size"] < 2000000)
  { 
      echo "<script type='text/jscript'>alert('File size is acceptable')</script>";
  }
  else
  {
      echo "<script type='text/jscript'>alert('File is too large')</script>";
      exit();
  }
  $directoryfile=move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target);

  if($result)
  {
      header("Location: login.html");
  }
  else
  {
      header("Location: register.html");
  }

 mysqli_close($conn);

}

当人们使用Php注册时，如何防止重复的用户名？

2 个答案: