how use data in PHP from ajax form - php

Question

My javascript code:
function _(selector){
return document.querySelector(selector);
}
function submitForm(){
var data = {
name: _("#name").value,
email: _("#email").value,
message: _("#message").value
}
var output = JSON.stringify(data)
var ajax = new XMLHttpRequest();
ajax.open( "POST", "/PATH" );
ajax.setRequestHeader("Content-type", "application/x-www-form-urlencoded")
ajax.onreadystatechange = function() {
if(ajax.readyState == 4 && ajax.status == 200) {
console.log('success')
} else {
console.log('fail')
}
}
console.log(output)
ajax.send(output);
}
When im trying do this with static data,it's work :
<?php
$name = "mateusz";
$to = "kaawkamateusz#gmail.com";
$subject = "kucharz";
$message = "message";
mail($to, $subject, $message);
?>
but, on example :
$name = $_POST["name"];
doesn't work.
Im trying use JSON but again, idk how get value from AJAX form in PHP.
Im never use PHP before, need help :)
EDIT
print_r show :
Array
(
[{"name":"asd","email":"asd#gmail_com","message":"12"}] =>
)

Answer 1

ajax.setRequestHeader("Content-type", "application/x-www-form-urlencoded")
You say you are sending URL encoded form data …
var output = JSON.stringify(data)
… but your data is JSON encoded.
To URL form encode it use URLSearchParams.
var data = {
name: "Example Name",
email: "example#example.com",
message: "This is a message"
}
var output = new URLSearchParams(data);
console.log(output.toString());
Note limited browser support. Consider using a polyfill.
Alternatively, set the correct content type for JSON and rewrite the PHP since JSON is not supported for $_POST.