https://github.com/mautic/mautic/issues/3463

mautic-test.php

<?php
define("AC_MAUTIC_URL", "https://mautic.example.org/");
define("AC_MAUTIC_USER", "myusername");
define("AC_MAUTIC_PASSWORD", "mypassword");

use Mautic\Auth\ApiAuth;
use Mautic\MauticApi;
require_once __DIR__ . '/vendor/autoload.php';

// ApiAuth->newAuth() will accept an array of Auth settings
$settings = array(
    'userName'   => AC_MAUTIC_USER,
    'password'   => AC_MAUTIC_PASSWORD
);

// Initiate the auth object specifying to use BasicAuth
$initAuth = new ApiAuth();
$auth = $initAuth->newAuth($settings, 'BasicAuth');
$api = new MauticApi();
$contactApi = $api->newApi('contacts', $auth, AC_MAUTIC_URL . "/api");

$fields = $contactApi->getFieldList();

// creating contact works fine:
$data = array('firstname' => 'API', 'companyemail' => 'mytest@example.org', 'ipAddress' => '127.0.0.1');
$response = $contactApi->create($data);
$new_contact = $response[$contactApi->itemName()];
var_dump($new_contact);

// read-only works fine:
$response = $contactApi->get($new_contact["id"]);
var_dump($response);


// updating contact doesn't work:
// Requested URL not found: /api/contacts/74577/edit
$updatedData = array(
    'firstname' => 'Updated Name'
);

$response = $contactApi->edit($new_contact["id"], $updatedData);
var_dump($response);