CodeIgniter $ this-> post（）获取不正确的字符串

I am writing a server script using CodeIgniter to store html code into database. My client send a json package contain a html string:

<table style='width:50%'

but from my server side I can only get from $this->post():

<table >

Do you know what wrong?

My full error log:

My JSON from the client side (encode by $.param from AngularJS):

apikey=superrocket_51f0c7333392f&faqid=31&categoryid=44&question=How+to+format+the+answer+%3F&answer=%3Ctable+style%3D'width%3A50%25%3B'%3E&displayorder=0

My PHP code to handle the JSON:

function updateFAQs_post(){
    $auth = $this->_auth();
    if ($auth){
        print_r($this->post('answer'));
        $this->load->model('Admin_model');
        $faqid = $this->Admin_model->updateFAQs($this->post('faqid'), $this->post('categoryid'), $this->post('question'), $this->post('answer'), $this->post('displayorder'));
        $response = array('success' => 'update done', 'faqid' => $faqid, 'index' => $this->post('index'));
        $this->response($response, 200);
    }
}

What I get from server:

<table >{"success":"update done","faqid":null,"index":false}

The faqid and index = null is expected. It has nothing to do with the error.

I think the error is due to the difference between the way JavaScript encode and the way PHP decode JSON package ?

I solved the problem by replacing $this->post('answer') by $_POST['answer'].

Still don't know that happened but it works

try

$this->input->post()

not $this->post()

$_POST works because thats raw php function

$this->post('answer');

Should be

$this->input->post('answer');