php-post-request.php

<?php
  const FORMAT_CONTENT_LENGTH = 'Content-Length: %d';
  const FORMAT_CONTENT_TYPE = 'Content-Type: %s';

  const CONTENT_TYPE_JSON = 'application/json';
  
  function HTTPJSONPost(string $url, array $params)
  {
    $content = json_encode($params);
    $response = file_get_contents($url, false, // do not use_include_path
         stream_context_create([
           'http' => [
             'method' => 'POST',
             'header' => [ // header array does not need '\r\n'
               sprintf(FORMAT_CONTENT_TYPE, CONTENT_TYPE_JSON),
               sprintf(FORMAT_CONTENT_LENGTH, strlen($content)),
             ],
             'content' => $content
           ]
         ])); // no maxlength/offset
    if ($response === false) {
      return json_encode(['error' => 'Failed to get contents...']);
    }
  
    return $response;
  }
  
  $url = "https://reqbin.com/echo/post/json";
  $data = [
    "Id" => 78912,
    "Customer" => "Jason Sweet",
    "Quantity" => 1,
    "Price" => 18.00,
  ];
  HTTPJSONPost($url, $data);