Dealing with Instagram APIs (JSON + PHP)

I'm new to PHP and I can't figure out how to deal with Instagram APIs in order to (for example) extract a list of links to the standard resolution images by recent 3 items published by the user_id 3.

Here's what I created till now:

<?php
 function get_instagram($user_id,$count)
 {
     $user_id = '3';
     $count = '3';
     $url = 'https://api.instagram.com/v1/users/'.$user_id.'/media/recent/?access_token=13137.f59def8.1a759775695548999504c219ce7b2ecf&count='.$count;
     $jsonData = $json_decode((file_get_contents($url)));
     $data = $jsonData->data;
     $result = '<ul>';
     foreach ($data as $key => $value) {
         $result .= '<li><a href='.$value->link.' ><img src="'.$value->images->standard_resolution->url.'" width="70" height="70" /></a></li> ';
     }
     $result .= '</ul>';
     return $result;
 }
 

The result is a blank page though.. can you help me?

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