I had to do this to make json_decode
work. Maybe there is a better scheme for this.
$j = $_POST["json"];
$j = str_replace("\\\\\"", "###dq###", $j);
$j = str_replace("\\", "", $j);
$j = str_replace("###dq###", "\\\"", $j);
or, in short:
$j = stripslashes($j);