电子邮件可用性检查返回可用的每一封电子邮件

表单提交的HTML代码:

<div class="control-group">
    <label class="control-label" for="input01">Email</label>
    <div class="controls">
         <input type="text" class="input-xlarge" id="email" name="email" 
         rel="popover" data-content="What’s your email address?" 
         data-original-title="Email">
        <span class="check" style="color:red;" ></span>
    </div>
</div>

将邮件发送到PHP脚本的代码:

 $(function () {
     $('#email').keyup(function () {
         var email = $(this).val();
         if (email != '') {
             //$('.check').show();
             $('error').fadeIn(400).html('<img src="/img/ajax-loading.gif" />');
             var dataString = 'email=' + email;
             $.ajax({
                 type: "POST",
                 url: "pages/check_email.php",
                 data: dataString,
                 cache: false,
                 success: function (result) {
                     if (result == '') {
                         $('.check').html(email + ' Avaliable');
                         $('#create').attr('disabled', '');
                         $('#create').attr('value', 'Active');
                         $("#email").removeClass("red");
                         $("#email").addClass("white");
                     } else {
                         $('.check').html(email + ' ' + result);
                         $('#create').attr('disabled', 'disabled');
                         $('#create').attr('value', 'Deactive');
                         $("#email").removeClass("white");
                         $("#email").addClass("red");
                     }
                 }
             });
         } else {
             $('.check').html('');
             $('#submit').attr('disabled', 'disabled');
             $('#submit').attr('value', 'Deactive');
         }
     });
 });

检查邮件可用性的代码，如果找到或没有找到值，返回1或0:

include_once "../base.php";
$stmt = $db->prepare("SELECT * FROM `Consultants` WHERE email =':email'");
$stmt->bindParam(":email", $_POST['email']);
$stmt->execute();
$num_rows = $stmt->fetchColumn();
$HTML='';
if($num_rows > 0){
    $HTML='is already used';
}else{
    $HTML='';
}
echo $HTML;
$stmt = null;

对于输入的每个电子邮件，它返回'available'。我有几个电子邮件在我的数据库，我正在使用。我在控制台也没有收到任何错误。

$stmt = $db->prepare("SELECT COUNT(*) FROM `Consultants` WHERE email =:email");