Facebook app connection code for PHP / WordPress

facebook_auth.php

<?php
define('FBAUTH_FB_OAUTH_URL', 'https://www.facebook.com/dialog/oauth');
define('FBAUTH_FB_OAUTH_TOKEN_URL', 'https://graph.facebook.com/oauth/access_token');
define('FBAUTH_FB_GRAPH_DEBUG_TOKEN_URL', 'https://graph.facebook.com/debug_token');
define('FBAUTH_FB_GRAPH_PROFILE_URL', 'https://graph.facebook.com/me');
define('FBAUTH_FB_APP_ID', 'xxxx');
define('FBAUTH_FB_APP_SECRET', 'xxxx');

function fbauth_get_fb_token($code) {
  global $post;
  $url = get_permalink($post->ID);

  $res = wp_remote_get( FBAUTH_FB_OAUTH_TOKEN_URL . 
                        '?client_id=' . FBAUTH_FB_APP_ID .
                        '&redirect_uri=' . urlencode($url) .
                        '&client_secret=' . FBAUTH_FB_APP_SECRET .
                        '&code=' . $code );

  if( strtoupper($res['response']['message']) != 'OK' )
    throw new Exception( __('Error 100: There was a problem communicating with Facebook. Try again later.') );

  parse_str($res['body']);

  if( !isset($access_token) )
    throw new Exception( __('Error 200: There was a problem communicating with Facebook. Try again later.') );

  setcookie('fbauth_fb_token',$access_token,(time()+(60*60*24*30)));
  $_COOKIE['fbauth_fb_token'] = $access_token;

  return $access_token;
}
  
function fbauth_get_fb_user($access_token) {
  $res = wp_remote_get( FBAUTH_FB_GRAPH_DEBUG_TOKEN_URL .
                        "?input_token={$access_token}" .
                        '&access_token='.FBAUTH_FB_APP_ID.'|'.FBAUTH_FB_APP_SECRET );

  $dbg = json_decode($res['body']);

  if( !isset($dbg->data->is_valid) or !isset($dbg->data->user_id) or $dbg->data->is_valid==0 )
    throw new Exception( __('Error 300: There was a problem communicating with Facebook. Try again later.') );

  return $dbg->data->user_id;
}

function fbauth_get_fb_profile( $tkn ) {
  $res = wp_remote_get( FBAUTH_FB_GRAPH_PROFILE_URL . "?access_token={$tkn}" );
  $prf = json_decode($res['body']);
  return $prf;
}

function fbauth_post_to_fb_feed( $user_id, $message ) {
  $fb_user_id  = get_user_meta( $user_id, 'fbauth_fb_user_id', true );
  //$fb_user_tkn = get_user_meta( $user_id, 'fbauth_fb_token', true );
  $fb_user_tkn = FBAUTH_FB_APP_ID.'|'.FBAUTH_FB_APP_SECRET;

  if( $fb_user_id !== false and $fb_user_tkn !== false ) {
    $url = "https://graph.facebook.com/{$fb_user_id}/feed";
    $args = array( 'body' => array( 'access_token' => $fb_user_tkn,
                                    'message' => strip_tags($message) ) );

    $res = wp_remote_post( $url, $args );
  }
}