is python request still able to post some data?

Question

I'm trying to post some data from a python client to a php web server. but php server is not receiving data. what did i do wrong?

my code

python client

import requests

url = 'http://localhost/datarecv.php'
mydata = {'somedata': 'mydata1233'}

p = requests.post(url, json = mydata)
print(p.text)

php Webserver

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    if (isset ($_POST['somedata'])) {
        $data = htmlspecialchars($_POST["somedata"]);
        $data = $_POST["somedata"];
        echo($data);
    } 
}