The code from http://w3lessons.info/2015/06/01/facebook-url-expander-with-jquery-ajax-and-php/ but less terrible.

FacebookUrlHelper.php

<?php

class FacebookUrlHelper
{
    private $graphApiUrl;
    
    private $fbHostname;

    public function __construct($graphApiUrl = 'http://graph.facebook.com', $fbHostname = 'facebook.com')
    {
        $this->graphApiUrl = $graphApiUrl;
        $this->fbHostname = $fbHostname;
    }
    
    public function getCoverImage($pageId)
    {
        $pageData = $this->getDataFromGraphApi("$pageId?fields=cover");
        return $pageData->cover->source;
    }
    
    public function getProfilePicture($pageId)
    {
        return $this->getDataFromGraphApi("$pageId/picture");
    }
    
    public function isValidUrl($facebookUrl)
    {
        if(!filter_var($facebookUrl, FILTER_VALIDATE_URL)) {
            return false;
        }
        $hostname = str_replace('www.', '', parse_url($facebookUrl, PHP_URL_HOST) );
        return ($hostname === $this->fbHostname);
    }
    
    public function getDataFromUrl($facebookUrl, $contentTypeKey = '')
    {
        $path = $this->getApiPathFromUrl($facebookUrl);
        $data = $this->getDataFromGraphApi($path);
        if($contentTypeKey) {
            $data[$contentTypeKey] = $this->getTypeFromData($data);
        }
        return $data;
    }
    
    public function getTypeFromData($apiData)
    {
        $hasLikes = isset($apiData->likes);
        $hasId = isset($apiData->id);
        
        if($hasLikes && $hasId) {
            return 'page';
        } elseif($hasId) {
            return 'profile';
        } else {
            return 'other';
        }
    }
    
    private function getApiPathFromUrl($facebookUrl)
    {
        if(!$this->isValidUrl($facebookUrl)) {
            throw new \InvalidArgumentException("The URL [$facebookUrl] is not a valid Facebook URL.");
        }
        $urlParts = parse_url($facebookUrl);
        $path = !empty($urlParts['path']) ? $urlParts['path'] : '';
        $path .= !empty($urlParts['query']) ?  '?' . $urlParts['query'] : '';
        return $path;
    }
    
    private function getDataFromGraphApi($path)
    {
        $url = $this->graphApiUrl . '/' . ltrim($path, '/');
        $response = file_get_contents($url);
        if(!$response) {
            throw new InvalidArgumentException("Unable to load data from the Graph API URL [$url].");
        }
        return json_decode($response);
    }
    
}

usage.php

<?php
$facebook = new FacebookUrlHelper();

if($facebook->isValidUrl($url)) {
    $data = $facebook->getDataFromUrl($url, '_type');
    
    if($type == 'profile') {
        echo get_profile_box($path, $data['name']);
    } elseif($type == 'page') {
        echo sprintf('<div class="fb-page" data-href="%s" data-width="500"></div>', $url);
    } else {
        echo sprintf('<div class="fb-post" data-href="%s"></div>', $url);
    }
}

echo '<img src="' . $facebook->getCoverImage('itzurkarthi') . '">';

echo '<img src="' . $facebook->getProfilePicture('itzurkarthi') . '">';