Php中的JSON无法正常工作

I have a problem and do not know what the problem is. I have a javascript variable in my html. which is:

  var people = '{"names": ["Matthew", "Lucas", "Todd", "Roxie", "Kyle", "Ken", "Gideon"], "surnames": ["Patel", "Lee", "Ingram", "Richter", "Katayanagi", "Katayanagi", "Graves"]}';

I parse the variable on one function in my script and use it. Everything works fine.

var mydata = JSON.parse(people);

But then I need to send the data to a php file, I send it by wrtting the data to a hidden input.

 var strObject = JSON.stringify(mydata);


var replaced = strObject.replace(/\//g, '');


oFormObject = document.forms['theForm'];
oFormObject.elements["jsonData"].value = replaced;

After which I try to encode it in my decode.php using:

$obj = $_POST['jsonData'];



json_decode($obj);
$s = stripslashes($obj);


var_dump($s); 

But when I do a var_dump($s) I get this output:

string(147) "{"names":["Matthew","Lucas","Todd","Roxie","Kyle","Ken","Gideon"],"surnames":["Patel","Lee","Ingram","Richter","Katayanagi","Katayanagi","Graves"]}"

Thus, I cannot output the contents in $s.Any suggestions.Please let me know if you need more information. BTW, its a homework assignment and I am stuck with the last section.

try saving json_decode($obj) to a variable and var_dump that something like

var $temp = json_decode($obj);
var_dump($temp);

the answer already is in the comments, but since this is the answer, i just post it as an answer.
you need to work with the return value from json_decode(). json_decode($obj) doesn't change the content of the variable $obj by itself:

$obj = $_POST['jsonData'];
$obj = json_decode($obj);
$obj = stripslashes($obj);


var_dump($obj); 

If you are looking for name surname pairs from json , you can try this

$a = '{"names": ["Matthew", "Lucas", "Todd", "Roxie", "Kyle", "Ken", "Gideon"], "surnames": ["Patel", "Lee", "Ingram", "Richter", "Katayanagi", "Katayanagi", "Graves"]}';
    $b = json_decode($a);
    $c = $b->names;
    $d = $b->surnames;
    for ($i = 0;$i< count($b->names); $i++){
        echo $c[$i]." ". $d[$i] ."<br>";
    }