遇到错误时问号会附加到URL吗？

Question

我有一张表格。当我提交并尝试在数据库中插入重复记录时，页面将重新加载并在控制台中记录错误消息。但是，在页面重新加载后，问号已经附加到URL的末尾。为什么会这样？

喜欢这个： http://localhost/project/home 对此（由于重复记录而发生数据库错误）： http://localhost/project/home?

控制器：

public function loadBoardManagement()
{
    $role     = $this->session->userdata('role');
    $user_id  = $this->session->userdata('user_id');
    $board_id = $this->uri->segment(3);

    $role = 'Admin';
    $user_id = 1;

    if ($this->uri->segment(3) == null)
    {
        $board_id = 178;    
    }

    if ($this->session->userdata('first_board_id') !== null && $board_id == 0) 
    { 
        $board_id = $this->session->userdata('first_board_id');
    }

    $data['boards']          = $this->Board_model->getBoards($role, $user_id);
    $data['board_assignees'] = $this->Team_model->getBoardAssignees($board_id);
    $data['all_teams']       = $this->Team_model->getAllTeams();
    $data['team_quantity']   = $this->Team_model->getBoardTeamsQuantity($board_id);
    $data['board_name']      = $this->Board_model->getBoardName($board_id);
    $data['board_id']        = $board_id;

    $this->load->view('board_management', $data);
}

public function fast_signup() 
{
    $username = $this->input->post('username');
    $password = $this->input->post('password');
    $first_name = $this->input->post('first_name');
    $last_name = $this->input->post('last_name');
    $email = $this->input->post('email');
    $role = $this->input->post('role');

    $fast_signup = $this->User_model->fastSignup($username, $password, $first_name, $last_name, $email, $role);

    if ($fast_signup)
    {
        echo 'success';
    }
    else
    {
        echo $fast_signup;
    }
}

的javascript：

function addMember()
{
    var username = $('#username').val();
    var password = $('#password').val();
    var first_name = $('#first_name').val();
    var last_name = $('#last_name').val();
    var email = $('#email').val();
    var role = $('#role option:selected').val();
    console.log('Role: ' + role);
    console.log(username + password + first_name + last_name + email);

    $.ajax({
        type: 'POST',
        url: base_url + 'user/fast_signup', //controller for inserting new members, but the current page is localhost/project/board/loadBoardManagement
        data: {
            'username': username,
            'password': password,
            'first_name':first_name,
            'last_name': last_name,
            'email': email,
            'role' : role
        },
        success: function(msg)
        {
            if (msg == 'success')
            {
                console.log('Member created');
                window.location.href = window.location.href;
            }
            else
            {
                console.log('Failed to create member!' + msg);
            }
        },
        error: function(jqXHR, textStatus, errorThrown)
        {
            console.log('Response: ' + jqXHR.responseText);
            console.log('Status code: ' + textStatus);
            console.log('Error thrown: ' + errorThrown);
        }
    });
}

$('#create_user_member').click(function() {
    addMember();
});