Javascript Fetch JSON PHP Complete Example

Save this to index.php and view this page in your browser.

This is the JSON before the fetch.

This is the JSON after the fetch.

Use "View Source" to see the html code.

Of course you can leave out the javascript and php code.

Here is the php code

<?php
  // Save this to json.php ------------------------------------------------------------------------
  $contentType = isset($_SERVER["CONTENT_TYPE"]) ? trim($_SERVER["CONTENT_TYPE"]) : '';

  if ($contentType === "application/json") {
    $content = trim(file_get_contents("php://input"));

    $decoded = json_decode($content, true);

    $decoded['bar'] = "Hello World AGAIN!";    // Add some data to be returned.

    $reply = json_encode($decoded);
  }  

  header("Content-Type: application/json; charset=UTF-8");
  echo $reply;
  // ----------------------------------------------------------------------------------------------
?>

Here is the javascript code

// Save this as fetch.js --------------------------------------------------------------------------

function success(json) {
  document.getElementById('after').innerHTML = "AFTER: " + JSON.stringify(json);
  console.log("AFTER: " + JSON.stringify(json));
} // ----------------------------------------------------------------------------------------------

function failure(error) {
  document.getElementById('after').innerHTML = "ERROR: " + error;
  console.log("ERROR: " + error);
} // ----------------------------------------------------------------------------------------------

function myButtonClick() {
  var url    = 'json.php';
  var before = {foo: 'Hello World!'};
  
  document.getElementById('before').innerHTML = "BEFORE: " + JSON.stringify(before);
  console.log("BEFORE: " + JSON.stringify(before));
  
  fetch(url, {
    method: 'POST', 
    body: JSON.stringify(before),
    headers:{
      'Content-Type': 'application/json'
    }
  }).then(res => res.json())
  .then(response => success(response))
  .catch(error => failure(error));
} // ----------------------------------------------------------------------------------------------