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php - 检查数据库中是否已存在用户名和电子邮件

问题描述

我刚开始使用 php，如果您键入已经存在的用户名或密码，我尝试创建系统以拒绝“创建帐户”。谢谢，抱歉我的英语不好。 我已经试过了。不工作：链接

这是我的 php：

<?php
session_start();

$db = mysqli_connect("localhost", "root", "", "itsnikola");

if (isset($_POST['register_btn'])) {
    $name = mysqli_real_escape_string($db, $_POST['name']);
    $lastname = mysqli_real_escape_string($db, $_POST['lastname']);
    $username = mysqli_real_escape_string($db, $_POST['username']);
    $email=mysqli_real_escape_string($db, $_POST['email']);
    $password=mysqli_real_escape_string($db, $_POST['password']);
    $password2=mysqli_real_escape_string($db, $_POST['password2']);

    if ($password == $password2) {
        session_start();
        $password = ($password);
        $sql="select * from account_info where (username='$username' or email='$email')";

        if (mysqli_num_rows($res) > 0) {
          $row = mysqli_fetch_assoc($res);
          if ($username==$row['username'])
          {
              $_SESSION['message'] = "Username je vec registrovan";
          }
          else($email==$row['email']){
              $_SESSION['message'] = "Email je vec registrovan"
          }
       else
        {
        $sql = "INSERT INTO users(name, lastname, username, email, password) VALUES('$name' , '$lastname' , '$username' , '$email' , '$password')";
        mysqli_query($db, $sql);
        $_SESSION['message'] = "Sada si ulogovan";
        $_SESSION['message'] = $username;
        header("location:login.php");
    }else {
        $_SESSION['message'] = "Ne podudaraju se lozinke!";
    }
}
?>

标签： phpmysqlvalidationemail

解决方案

您在此行之前错过了非常重要的行if (mysqli_num_rows($res) > 0)

$sql="select * from account_info where username='$username' or email='$email' ";

$res = mysqli_query($db, $sql); // you're missing this line to query by $sql 

if (mysqli_num_rows($res) > 0) {
// you're other code goes here 
}

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