php - 使用 Ajax 和 PHP 检查数据库中的现有用户

Question

我遇到了一个问题，代码不断显示用户名可用，即使它存在于数据库中。任何人都可以解决我遇到的问题吗？下面是我的代码。

PHP

    // Define $username
    $username=$_POST["emailAddress"];

    // Create Connection
    $db = new mysqli($server, $user, $password, $database);

    // Check Connection
    if ($db->connect_error) {
        die("Connection failed: " . $db->connect_error);
    }

    // SQL query to fetch registerd users and finds user match.
    $query = "SELECT email_address FROM users WHERE email_address='$username'";

    $result = mysqli_query($db,$query);    
    $rows = mysqli_num_rows($result);

    //if number of rows fields is bigger them 0 that means it's NOT available '  
    if($rows>0){  
    //and we send 0 to the ajax request  
        echo 0;  
    }else{  
    //else if it's not bigger then 0, then it's available '  
    //and we send 1 to the ajax request  
        echo 1;  
    }  
    mysqli_close($db); // Closing Connection

jQuery

$(document).ready(function () {

//when button is clicked  
$('[name="checkAvail"]').on("click", function () {
    check_availability();
});

});

//function to check username availability  
function check_availability() {

//get the username  
var username = $('[name="emailAddress"]').val();

//use ajax to run the check  
$.post("checkusers.php",
    function (result) {
        //if the result is 1  
        if (result == 1) {
            //show that the username is available  
            $('.existingUser').html(username + ' is Available');
        } else {
            //show that the username is NOT available  
            $('.existingUser').html(username + ' is NOT Available');
        }
    });

}

HTML

         <div class="form-group">
        <button class="btn btn-default" name="checkAvail">Check Availability</button>
        <label for="emailAddress" class="col-sm-5 control-label">Email:</label>
        <div class="col-sm-4">
            <input type="email" class="form-control" id="emailAddress" name="emailAddress" placeholder="Email" autocomplete="off">
        </div>
    </div>

Answer 1

你的ajax不发送任何数据...所以$_POST["emailAddress"];在你的php中将为空

您需要添加一个数据对象作为$.post的第二个参数

$.post("checkusers.php",{emailAddress : username },function (result) {
     // success handing code left out for clarity
});

此外，在允许用户检查输入之前，您应该检查输入是否不为空。向服务器发送无效的空值没有意义。

您可以使用许多简单的 JavaScript 验证插件。

同样，服务器上应该验证用户输入。这是最重要的验证点，因为可以解决 JavaScript 允许发送任何内容