Get transformed asset URL in controller
You'd do it from PHP nearly idential to how you'd do it from Twig... by passing in the Asset Transform's handle to AssetFileModel's getUrl() method.

Twig:

{% set asset = craft.assets.id(1).first() %}

{% if asset %}
    {{ asset.getUrl('myTransform') }}
{% endif %}


PHP:

$criteria = craft()-&gt;elements-&gt;getCriteria(ElementType::Asset);
$criteria-&gt;id = 1;
$asset = $criteria-&gt;first();

if ($asset)
{
    $url = $asset-&gt;getUrl('myTransform');
}