检查用户名存在于数据库与AJAX [英] Check if username exists in database with AJAX

问题描述

因此​​，基本上，我想将功能添加到我的登记表，我会检查，如果该用户名已经存在于数据库中。

So basically, I want to add a feature to my registration form which I will check if that username already exists in the database.

我有关于AJAX的几个问题 -

I have a few questions about AJAX -

1）我想创建一个AJAX请求on_change功能，所以像这样 -

1) I want to create an AJAX request on_change function, so something like this -

$('#username').change(function() {
  $.ajax({
  url: "validation.php"
  });
});

所以，据我了解，我必须做在PHP中validation.php文件中的所有验证，正确吗？有没有需要任何特殊的验证还是可以只是简单的验证和SQL语句 - SELECT * FROM'用户'WHERE'用户名'='。 $ _ POST [用户名];

2），所以我的理解，我必须通过$就通过POST值太大，是否正确？如果是的话，我将如何能够通过validation.php文件来访问它们？

2) So as I understood I must pass the POST values via $.ajax too, correct? If yes, how will I be able to access them via the validation.php file?

3）后，我得到的结果validation.php文件，我怎么能传回（真或假的 - 的存在或不存在）？我需要将它们传回，然后如果检查做了，如果这是真的 - ？显示的用户名已经存在一个错误，否则，不显示任何东西。

3) After I get the results in validation.php file, how can I pass them back (true or false -- exists or doesn't exist)? I will need to pass them back, and then do an if check, if it's true - show an error that the username already exists, otherwise, don't show anything?

希望，你明白我要创建。我知道有很多教程在互联网上，但我不喜欢创造，通过教程的东西，因为如果我通过自己创建它，它会更容易理解接下来的时间;！）

Hope, you understood what I'm about to create. I know there are a lot of tutorials over the internet, but I don't like to create something via tutorials, since if I create it by myself, it will be easier to understand next time ;)!

编辑：另外，我创建自己的网站以codeIgniter框架，因此，我将如何通过url属性在阿贾克斯，在codeIgniter模块

In addition, I'm creating my website with CodeIgniter framework, so how would I pass the url attribute in ajax, to a CodeIgniter module?

推荐答案

在继续， SELECT * FROM'用户'WHERE'用户名'='。 $ _ POST [用户名]; 只是要求一个SQL注入。我建议你​​使用PHP数据对象 - http://php.net/manual/en/book.pdo.php 。

Before continuing, SELECT * FROM 'users' WHERE 'username' = '. $_POST['username']; is just ASKING for a SQL Injection. I suggest you use PHP Data objects - http://php.net/manual/en/book.pdo.php.

所以我的理解，我必须通过$就通过POST值太大，是否正确？如果是的话，我将如何能够通过validation.php文件来访问它们？

由于这是一个简单的要求，我建议你使用jQuery的方法 $。员额（）。下面是一个示例基于关闭你正在尝试做的事情。

Because this is a simple request, I suggest you use JQuery's method $.post(). Here's a sample based off of what you're trying to do.

$.post('validation.php',{username: $('#username').val()}, function(data){
    if(data.exists){
        //tell user that the username already exists
    }else{
        //username doesn't exist, do what you need to do
    }
 }, 'JSON');

jQuery的POST方法需要4个参数 $。员额（网址，数据，回调，数据类型）。在上面的例子中，我们将发布与 $（'＃用户名）的用户名。VAL（）到 validation.php 并期望 JSON 响应。当请求完成后，回调函数将与数据执行是从请求的响应。因为我们指定的响应将是 JSON ，我们可以访问它，就像在JavaScript原生对象。现在，让我们看一下validation.php

jQuery's post method takes 4 parameters $.post(url, data, callback, datatype). In the example above, we will be posting the username with $('#username').val() to validation.php and expect a JSON response. When the request is finished, the callback function will be executed with data being the response from the request. Because we specified that that response will be JSON, we can access it just like a native object in javascript. Now let's move to validation.php

就像我上文所述，我建议你使用PDO的数据库驱动程序。因此，在这个例子中，我会告诉你它的基本用法。

Like I stated above, I suggested you use PDO for your database driver. So in this example, I will show you a basic usage of it.

//set the headers to be a json string
header('content-type: text/json');

//no need to continue if there is no value in the POST username
if(!isset($_POST['username']))
    exit;

//initialize our PDO class. You will need to replace your database credentials respectively
$db = new PDO('mysql:host=DATABASE_HOST;dbname=DATABASE_NAME','DATABASE_USERNAME','DATABASE_PASSWORD',array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));

//prepare our query.
$query = $db->prepare('SELECT * FROM users WHERE username = :name');
//let PDO bind the username into the query, and prevent any SQL injection attempts.
$query->bindParam(':name', $_POST['username']);
//execute the query
$query->execute();

//return the json object containing the result of if the username exists or not. The $.post in our jquery will access it.
echo json_encode(array('exists' => $query->rowCount() > 0));

现在回顾一下，我们的jQuery脚本将张贴到 validation.php 它从数据库中选择一个用户名。它会返回一个 JSON 对象，它具有的项存在这是一个布尔值，表示如果该用户名已经存在，作为一个排在你的数据库。当请求完成后通过jQuery，您可以您所需要的基础关闭查询结果做的。我希望这是一个彻底的解释，并引导你到你希望什么来完成。

Now to recap, our jQuery script will post to validation.php where it selects a username from the database. It will return a JSON object that has a key of exists that is a boolean indicating if the username already exists as a row in your database. When the request is complete via jQuery, you can do what you need based off the result of the query. I hope this is a thorough explanation and leads you to what you are hoping to accomplish.

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