CodeIgniter：致命错误：无法在写上下文中使用方法返回值

I have this issue where I am posting a response into the controller, however it throws this error. This is the first time I am coming across this error.

Kindly find the code below:

    if (isset($this->input->post('responseCode'))) 
       {
         echo '<p><strong>Cardstream Response</strong></p>';
         echo '<pre>';
         print_r($this->input->post());
         echo '</pre>';
       }

It is pointing at this particular line if (isset($this->input->post('responseCode')))

This is a cardstream integration. Unfortunately I haven't found the library for cardstream in codeigniter, hence I am using the Core PHP code for the same.

Any help will be greatly appreciated. Thanks.

You are using isset() on a method, which presumably returns a expression result. You cannot do that because isset() is only used on variables. Try checking if it's null instead:

if ($this->input->post('responseCode') !== null) {...

Or simply:

if ($this->input->post('responseCode')) {...

Use this

if ($this->input->post('responseCode'))

instead isset() checking

you cant use isset on a function you couldusse

if($this->input->post('responsecode'))

or if(!empty($this->input->post('responsecode')))