Question

任何人都可以帮我解决这个代码到底出错的地方吗？当我试图检查数据库中是否已存在电子邮件时，我错了。

如何检查数据库中是否存在电子邮件？

       <html>
        <h1> Registration Form </h1>
        <body>
        <form method="post" action="">
       <input type="text" name="fname" placeholder="first name" required><br><br>
       <input type="text" name="lname" placeholder="last name" required><br><br>
       <input type="text" name="mail" placeholder="mail" required> <br><br>
       <input type="PASSWORD" name="pass1" placeholder="password" required> <br><br>
       <input type="PASSWORD" name="pass2" placeholder="repeat password" required> <br>   <br>
       <input type="submit" name="submit">
         </form>


         <?php
         if(isset($_POST['submit']))
           {
       $fname = $_POST['fname'];
       $lname = $_POST['lname'];
       $mail =  $_POST['mail'];
       $pass1 =  $_POST['pass1'];
       $pass2 =  $_POST['pass2'];
       if($pass1 !== $pass2)
        {
      echo "password in correct ";
         }
      else
         { 
      $db = mysqli_connect("localhost","root","","reviewsystem");
      $check = "SELECT * FROM registers WHERE $mail = email";
      if($check == TRUE){
      echo "email already exists";
          }
       else{
      $query = "INSERT INTO registers(fname,lname,email,password)   VALUES('$fname','$lname','$mail','$pass1')";
       mysqli_query($db,$query);
         echo "  you are registered succesfully";
            }
           }
          }
         ?>


    </body>
    </html>

Answer 1

首先要做的是：您没有执行任何类型的查询。你刚刚创建了一个字符串。添加一行：

$db = mysqli_connect("localhost","root","","reviewsystem");
$check = "SELECT * FROM registers WHERE $mail = email";
$result = mysqli_query($db, $check); //i think there is a typo, mysqi_query

之后，您可以使用mysqli_num_rows返回从DB返回的SELECT行数，以确定该条目是否已存在：

 if(mysqli_num_rows($result) > 0){
     echo "email already exists";
 }

Answer 2

问题出在你的mysql查询的where子句中。你必须把它写成

$check = "SELECT * FROM registers WHERE email = '".$mail."'"; if($check == TRUE){ echo "email already exists"; } else{

试图检查已经在数据库中的用户输入的邮件

2 个答案: