Instafeedjs - how to give each picture different size

I'm using Instafeed.js (http://instafeedjs.com) to collect images from Instagram and show them on my website. But how do I control the size of each picture, and control whether it's in low-resolution or standard resolution?

<script type="text/javascript">
    var userFeed = new Instafeed({
        get: 'user',
        userId: userID,
        accessToken: 'accessToken',
        resolution: 'standard_resolution',
        template: '<a href="{{image}}"><img src="{{image}}" /></a>'
        });
    userFeed.run();
</script>

In the past I used this code, but it doesn't work anymore:

<?php
// Supply a user id and an access token
$userid = "userID";
$accessToken = "acessToken";

// Gets our data
function fetchData($url){
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_TIMEOUT, 20);
    $result = curl_exec($ch);
    curl_close($ch); 
     return $result;
}

// Pulls and parses data.
$result = fetchData("https://api.instagram.com/v1/users/2254178/media/recent/?access_token=2254178.467ede5.4cf795f92f0a49b68724a782e706f6b5");
$result = json_decode($result);
?>

<?php $x = 1; ?>
if($x == 1) { 
    echo'<a class="group left big" rel="group1" href="'.$post->images->standard_resolution->url.'"><img src="'.$post->images->standard_resolution->url.'"></a>';
    $x = 2; 
}

else if($x == 2) {
    echo'<a class="group left small" rel="group1" href="'.$post->images->standard_resolution->url.'"><img src="'.$post->images->low_resolution->url.'"></a>';
    $x = 3; 
}