检查数据库中是否已经存在用户名和电子邮件

时间：2018-10-20 13:34:13

标签： php mysql validation email username

我刚开始使用php，并且尝试创建系统以拒绝“创建帐户”（如果您键入现有的用户名或密码）。谢谢，对不起我的英语不好。 我已经尝试过。无法正常工作：link

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!";
    }
}
?>

3 个答案:

答案 0 :(得分：1)

您在此行if (mysqli_num_rows($res) > 0)之前错过了非常重要的一行

$sql="select * from account_info where username='$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 
}

答案 1 :(得分：0)

首先，session_start()被呼叫2次。
删除if ($password == $password2) {内部的重复呼叫
您的代码也缺少;和一些}（用于正确关闭if条件）

现在解决方案：
在处理数据库查询的结果之前，需要连接到数据库并执行适当的SQL命令，然后您才能获得所需的结果。您的代码缺少此过程。
在下面的代码中检查我的评论↓，然后在更正的代码中再次检查

if ($password == $password2) {
        session_start(); // remove this repeated call
        $password = ($password);
        $sql="select * from account_info where (username='$username' or email='$email')";
        if (mysqli_num_rows($res) > 0) { // $res isn't defined
          $row = mysqli_fetch_assoc($res);
          if ($username==$row['username'])
          {
              $_SESSION['message'] = "Username je vec registrovan";
          }
          else($email==$row['email']){  // `else` doesn't work this way, use `elseif`
              $_SESSION['message'] = "Email je vec registrovan"  // ; missing
          }


更正的代码：

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) {
        $password = ($password);
        $sql      = "SELECT * FROM users WHERE (username='$username' OR email='$email')";
        $res      = mysqli_query($db, $sql); // you were calling $res but it wasn't defined; this connects to the DB and executes SQL and then assigns the result
        if (mysqli_num_rows($res) > 0) {
            $row = mysqli_fetch_assoc($res);
            if ($username == $row['username']) {
                $_SESSION['message'] = "Username je vec registrovan";
            } elseif ($email == $row['email']) {  // changed `else` to `elseif` to include the condition, `else` doesn't accept conditional checks
                $_SESSION['message'] = "Email je vec registrovan";  // added ;
            }
        } else {
            $sql = "INSERT INTO users (name, lastname, username, email, password) VALUES ('$name', '$lastname', '$username', '$email', '$password')";
            if (mysqli_query($db, $sql)) {
                // New record inserted
                $_SESSION['message'] = "Sada si ulogovan";
                $_SESSION['message'] = $username;
                header("location: login.php");
            } else {
                echo("Error: " . mysqli_error($db));
            }
        }
    } // required to close the password checking condition
    else {
        $_SESSION['message'] = "Ne podudaraju se lozinke!";
    }
}
  

建议：

     
      
  1. 使用准备好的语句，而不是直接将用户提供的输入传递给SQL
    （关键，当前的代码容易受到SQL注入的攻击）
    2.   
  2. 使用支持PHP并提供语法高亮显示的IDE（Atom，Visual Studio Code，PhpStorm等）
    3.   

答案 2 :(得分：0)

我已经尝试过了

<?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) {
        $password = ($password);
        $sql      = "select * from account_info where (username='$username' or email='$email')";
        $res      = mysqli_query($db, $sql); // you were calling $res but it wasn't defined; this connects to the DB and executes SQL and then assigns the result
        if (mysqli_num_rows($res) > 0) {
            $row = mysqli_fetch_assoc($res);
            if ($username == $row['username']) {
                $_SESSION['message'] = "Username je vec registrovan";
            } elseif ($email == $row['email']) {  // changed `else` to `elseif` to include the condition, `else` doesn't accept conditional checks
                $_SESSION['message'] = "Email je vec registrovan";  // added ;
            } 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'] = $username;
                header("location:login.php");
            }
        } // required to close `if (mysqli_num_rows($res) > 0)`
    } // required to close the password checking condition
    else {
        $_SESSION['message'] = "Ne podudaraju se lozinke!";
    }
}
?>

但无法正常工作错误代码：

  

警告：mysqli_num_rows（）期望参数1为mysqli_result，   在第17行的Z：\ Programs \ XAMPP \ htdocs \ register.php中给出的布尔值

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