Php extracts the special symbols passed by post.

Php retrieves the special symbols passed by post. the front-end page has a check box (multiple choice) with the following code: & lt; select & nbsp; namelevel & nbsp; data-options & nbsp; multiple: true & nbsp; & gt php retrieves special symbols passed by post
The code of the check box (multiple choice) on the front-end page is as follows:

        All Level        A        B        C        D    

Retrieve the background page with post

$level =isset($_POST['level'])? implode("",$_POST['level']):"'A+','A-','A','B','C','D'";

I want to use the SQL in statement to query data in the database, but the problem is that the passed value SQL always reports an error. I printed it and found that the value received in the background seems to be an array,

I would like to ask how to get the correct multiple selection values from the front?
------ Solution --------------------
Print_r ($ _ POST ['level']);
View Results
------ Solution --------------------

------ Solution --------------------
Echo date ('Y-m-d H: I: S', strtotime ("$ datea-1 year "));