Simple example to post to a Facebook fan page via PHP?

<?php

require_once __DIR__ . '/vendor/autoload.php';

$fb = new \Facebook\Facebook([
  'app_id' => 'YOUR_APP_ID',
  'app_secret' => 'YOUR_APP_SECRET',
  'default_graph_version' => 'v19.0',
]);

$pageAccessToken = 'YOUR_PAGE_ACCESS_TOKEN';

try {
  $response = $fb->post(
    '/YOUR_PAGE_ID/feed',
    [
      'message' => 'Hello, world!',
    ],
    $pageAccessToken
  );
} catch (\Facebook\Exceptions\FacebookResponseException $e) {
  echo 'Graph returned an error: ' . $e->getMessage();
  exit();
} catch (\Facebook\Exceptions\FacebookSDKException $e) {
  echo 'Facebook SDK returned an error: ' . $e->getMessage();
  exit();
}

$graphNode = $response->getGraphNode();

if ($response->getStatusCode() == 200) {
  echo 'Successfully posted! Post ID: ' . $graphNode->getField('id');
} else {
  echo 'Failed to post.';
}