If you are not using dataType : 'json', you might need to do stripslashes

$.post(window.data.baseUrl, {posts : JSON.stringify(posts)});

And in php:

$posts = json_decode(stripslashes($_POST['posts']));

First off, it's worth pointing out that PHP is not "messing up" anything. It's escaping characters, which may look weird, but it is perfectly valid and when you json_decode it later it will be just the same as it was originally. See here: https://3v4l.org/Smj2F

If you don't like the escaping though, you can use the JSON_UNESCAPED_UNICODE flag:

https://www.php.net/function.json-encode

This flag will "encode multibyte Unicode characters literally" according to https://www.php.net/manual/en/json.constants.php.

So you can do:

json_encode($array, JSON_UNESCAPED_UNICODE);

And it will give you the following output:

["M-am întîlnit ieri cu","fosta mea profă de matematică"]

Working example: https://3v4l.org/daETG

You need to JSON.parse() your valid JSON string.

var str = '{"hello":"world"}';
try {
  var obj = JSON.parse(str); // this is how you parse a string into JSON 
  document.body.innerHTML += obj.hello;
} catch (ex) {
  console.error(ex);
}

Use json_decode to decode a json array in PHP

 $data = json_decode($_POST['data']);

http://php.net/manual/en/function.json-decode.php

Use the function json_encode() to create a json string again (as it returns string):

$myJsonString = json_encode($my_decoded_json);

I think you want to use something like

'posted_data=' + encodeURIComponent(JSON.stringify(tickets))

Then, on the PHP side you can get it with

$posted_data = $_POST['posted_data'];
$data = json_decode($posted_data);

Instead of using JSON.stringify, you could also use the JSON as the data and jQuery will convert it to a query string as part of the request. Then, you can use the individual components in $_POST.

When you save some data using JSON.stringify() and then need to read that in php. The following code worked for me.

json_decode( html_entity_decode( stripslashes ($jsonString ) ) );

Thanks to @Thisguyhastwothumbs