用户类未在数据库中以false形式返回重复的电子邮件

我创建了一个用户类，用于验证通过表单传递的数据，然后更新数据库表用户。我想添加额外的功能，例如检查表中是否存在用户名和电子邮件，我已经从stackoverflow的成员那里获得了一些帮助，以便开始构建它，但是下面的代码仍然允许将重复的电子邮件插入数据库，我没有收到任何sql错误消息，只有一条成功消息，如下所示"插入1行"。"很明显，我预计错误消息"电子邮件存在"

任何帮助都会有帮助。

public function insert() {
$result = $this->mysqli->prepare("SELECT COUNT(*) FROM users WHERE email=?");
$result->bind_param("s", $_POST['email']);
$result->execute();
$result->bind_result($email_count);
$result->close();   
if ($email_count > 0) {
echo "email exisits!";
} else {
//escape the POST data for added protection
    $username = isset($_POST['username']) ? $this->mysqli->real_escape_string($_POST['username']) : '';
    $cryptedPassword = crypt($_POST['password']);
    $password = $this->mysqli->real_escape_string($cryptedPassword);
    $name = isset($_POST['name']) ? $this->mysqli->real_escape_string($_POST['name']) : '';
    $email = isset($_POST['email']) ? $this->mysqli->real_escape_string($_POST['email']) : '';
    $stmt = $this->mysqli->prepare("INSERT INTO users (username, password, name, email) VALUES (?, ?, ?, ?)");
    //var_dump($this->mysqli->error);
    $stmt->bind_param('ssss', $username, $password, $name, $email); // bind strings to the paramater
    /* execute prepared statement */
    $stmt->execute();
    printf("%d Row inserted.'n", $stmt->affected_rows);
    /* close statement and connection */
    $stmt->close();
                } // end email_count and insert to table
            } // end function

我使用了下面所附的ajax代码，它对我很有用。。。。如果有用的话就试试。。。。

ajax代码------------------

   <script type="text/javascript">
    $(document).ready(function() {
        // check username availability on focus lost
        $('#username').focusout(function() {
           if ($('#username').val()!='') {
               var username=$('#username').val();
           $.ajax({
                    url: "/gtlqa/checkUserNameAvailability/checkAvailability.html?username="+username,
                    method:'GET',
                    success:function(data){
                        if(data!="available")
                            {
                             $('input:submit').attr("disabled", true);
                             $("#usernameErrorMessage").html("username already exists");
                            }
                        else
                            {
                            $("#usernameErrorMessage").html("available");
                            $('input:submit').attr("disabled", false);
                            }
                        }
               });
            }
        });
    });
    function checkAvailability() {
        $.getJSON("/checkUserNameAvailability", {
            username : $('#username').val()
        }, function(available) {
            if (available) {
                fieldValidated("username", {valid : true});
                $('input:submit').attr("disabled", false);
            } else {
                $('input:submit').attr("disabled", true);
                fieldValidated("username", {valid : false, message : $('#username').val() + " is not available"});
            }
        });
    }
 </script>

控制器----------------

@RequestMapping(value="checkAvailability",method = RequestMethod.GET)
public @ResponseBody String getAvailability(@RequestParam("username") String username) {
    System.out.println("username is"+username);
    boolean status=userService.available(username);
    if(status)
    {
    return "available";
    }
    else 
    return "username already exists";
}