<?php
$raw = file_get_contents('php://input');
// echo $raw;  username=potchara&password=1234
parse_str($raw, $parsed);
// echo json_encode($parsed); // {"username":"potchara", "password":"1234"}
$data = json_encode($parsed);
// $data will be json string
$data = json_decode($data);

echo $data->password;
?>