php - 通过php检查用户名是否存在于mysql表中？

Question

这个问题已经有答案了:

Check if value exists before inserting into MySQL DB in a PHP script (1 个回答)

How to check if a row exists in MySQL? (i.e. check if username or email exists in MySQL) (4 个回答)

已关闭 9 年前。

我试图弄清楚如何让我的注册php代码检查注册者的用户名是否已被占用，如果是，则不要注册它，告诉用户它已被占用。这是我的整个寄存器处理文件。

<?php
$con=mysqli_connect("localhost","root","","users");
// Check connection
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }

$hpassword = hash( 'sha512', $_POST['password'] );
$eusername = mysqli_real_escape_string( $con, $_POST['username'] );
$eemail = mysqli_real_escape_string( $con, $_POST['email'] );
$fusername = str_replace(' ', '', $eusername);

$sql="INSERT INTO users (username, password, email)
VALUES
('$fusername','$hpassword','$eemail')";

if (!mysqli_query($con,$sql))
  {
  die('Error: ' . mysqli_error($con));
  }
mysqli_close($con);
?> 

Answer 1

$sql=mysql_query("SELECT FROM users (username, password, email) WHERE username=$fusername");
 if(mysql_num_rows($sql)>=1)
   {
    echo"name already exists";
   }
 else
    {
   //insert query goes here
    }

您可以从数据库检查用户是否存在，然后粘贴代码