passing json object with ajax to php - php

Question

I have set up a basic api and I know its working because requests that come with postman pass normally ,what I am having trouble with is passing the JSON object through AJAX to the php file.
The AJAX part
function add_book(){
if(validate()){
var jsonData = {};
jsonData.Price = document.getElementsByName("Price")[0].value;
jsonData.Title = document.getElementsByName("Title")[0].value;
jsonData.Author = document.getElementsByName("Author")[0].value;
jsonData.Genre = document.getElementsByName("select_dropdown")[0].value;
alert(JSON.stringify(jsonData));
var request = new XMLHttpRequest();
var url = "/books.php";
request.open("POST", url, true);
request.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
request.onreadystatechange = function() {
if (request.readyState == 4 && request.status == 200) {
}
}
request.send(jsonData);
}
}
For example this is the alert I get from stringifying the object
{"Price":"23","Title":"asdas","Author":"dasda","Genre":"Science fiction"}I can basically copy/paste this string to postman and it works as intended.
Now to the php part
$json_str = file_get_contents('php://input');
$json_obj = json_decode($json_str);
if(!empty($json_obj->Price) && !empty($json_obj->Genre) && !empty($json_obj->Author) && !empty($json_obj->Title)){
The if always returns false ,while it should not ,again postman requests pass for true.
========================================================================
EDIT :
I managed to find the source of the problem . I made a function to check if the json is valid , turns out its not , there is no problem in the php part as it turns out . Here is the function in case someone needs it / wonders :
function isValidJSON($str) {
json_decode($str);
return json_last_error() == JSON_ERROR_NONE;
}
=========================================================================Edit 2:
The problem was on the request.send(jsonData); part . Fixed it with request.send(JSON.stringify(jsonData));
Thanks for your time !

Answer 1

This is the problem
$json str = file_get_contents('php://input');
The post parameters should be accessed by $_POST.
Instead try this
$json_str = $_REQUEST['jsonData']`;
and also do a var_dump for $json_str

Answer 2

Does this help?
$json_str = file_get_contents('php://input');
$json_obj = json_decode($json_str);
if(!empty($json_obj['Price']) && !empty($json_obj['Genre']) && !empty($json_obj['Author']) && !empty($json_obj['Title'])){

Answer 3

I think the problem is the file_get_contents(). Maybe you try to echo it.
And for the if you could write:
if (!(empty($json_obj->Price) && empty($json_obj->Genre) && empty($json_obj->Author) && empty($json_obj->Title)))