PHP POST ARRAY to json_encode

Question

I want to use JSON to store the value into Mysql cuz I am making a quiz and there are many answers. But it doesn't go well. Please tell me what's wrong.THX!

<form  method="post" action="resultme.php">
     <h4>   Q1 </h4>
      <input name="a[0][]" type="radio"  value="1" /><span>Yes</span> 
      <input name="a[0][]" type="radio"  value="2" /><span>maybe</span> 
      <input name="a[0][]" type="radio"  value="3" /><span>No</span>   
     <h4>   Q2 </h4>
        <input name="a[1][]" type="radio"  value="1" /><span>Yes</span> 
         <input name="a[1][]" type="radio" value="2" /><span>Maybe</span> 
         <input name="a[1][]" type="radio" value="3" /><span>No</span> 
    <h4> Q3 </h4>
        <li class="ji">Language</li>
        <li><input name="a[2][]" type="checkbox"  value="11" /><span>English</span></li>
        <li><input name="a[2][]" type="checkbox"  value="12" /><span>Chiness</span></li>
          <li class="ji">Sport</li>
          <li><input name="a[2][]" type="checkbox" value="21" /><span>swim</span></li>
         </ul>
<input type="submit" value="click" name="submit" />

How to get the POST thing? Here is my thought below to get each answer then I can json with {} But it' no use.

$ans   =array(  "q1"=> $_POST['a[0]'],
        "q2"=> $_POST['a[1]'],
        "q3"=> $_POST['a[2]'],
            )
print_r json_encode( $ans );

Answer 1

1. to debug, just print_r($_POST); after you submit so you will see the structure

2. try

   $ans = array();

   foreach($_POST['a'] as $idx => $answer)

   {

   $ans['q'.($idx+1)] = $anwser;

   }

   $ans = json_encode( $ans );