PHP gets JSON String as array

Question

I have a form with 17 checkboxes. When one of these changes, JavaScript should submit the values to the server (running PHP).

I want to use JSON, because the checkboxes give two arrays which have to be seperated in PHP

In JS, I create an JSON-String, which I want to submit via POST and read and decode in PHP. The String looks like this atm: [["2015-06-26","2015-06-27"],["2","3","4","5","6","7","8","9","10","11","12","13","14"]] - This is what I want it to be.

This is, what my AJAX-function looks like:

var fullArray = [dateArray, trackArray];
var jsonFullString = JSON.stringify(fullArray);
//jsonFullString == [["a","b","c"],["d","e","f","g"]]
$.ajax({
  type:'POST',
  url:'shownitems.php',
  data: jsonFullString,
  success: function(data){
    //More script. This comment is reached, because
    alert(data);
    // works.
  }
});

When I get it to PHP, and search for $_POST[0] the success function in JS doesn't show anything. When I search for $_POST, I get "Array.." back.

This is, what my PHP looks like (This is my test snippet):

<?php
echo $_POST;
echo ".";
echo $_POST[0];
echo ".";
echo $_POST[0][0];
$array = array();
?>

I am also using jQuery.

Answer 1

In your JS:

/* dateArray and trackArray must be variables with values */
$.ajax({
  method: "POST",
  url: "shownitems.php",
  data: { date: dateArray, track: trackArray }
}).done(function(response) {
  alert(response);
});

In your PHP:

<?php 
  var_dump('Date: '.$_POST['date']);
  var_dump('Track: '.$_POST['track']);
?>

Answer 2

You should get your request content instead the $_POST variables.

Something like this would

$json = file_get_contents('php://input');
$obj = json_decode($json); //Will contain your array of two arrays

In case you wanted to get your post variables like you are doing, you could change your AJAX request and use:

$.ajax({
  type:'POST',
  url:'shownitems.php',
  data: {
    data: jsonFullString
  },
  success: function(data){
    //More script. This comment is reached, because
    alert(data);
    // works.
  }
});

And your PHP would be:

$json = $_POST["data"];
$obj = json_decode($json); //Will contain your array of two arrays