Converter textos em Imagens, Videos e Links

gistfile1.aw

<?php
$str = 'This is an image: google.ca/images/srpr/logo3w.png<br>

YouTube: http://www.youtube.com/watch?v=V2b8ilapFrI&feature=related <br>

Stackoverflow:  http://stackoverflow.com/';

function converterLinksEmVideos($arr){
	
	if(strpos($arr[0], 'http://') !== 0){
		$arr[0] = 'http://' . $arr[0];
	}
	
	$url = parse_url($arr[0]);

	// images
	if(preg_match('#\.(png|jpg|gif)$#', $url['path']))	{
		return '<img src="'. $arr[0] . '" />';
	}
	
	// youtube
	if(in_array($url['host'], array('www.youtube.com', 'youtube.com')) && $url['path'] == '/watch' && isset($url['query']))	{
		parse_str($url['query'], $query);
		return sprintf('<img src="http://img.youtube.com/vi/%s/2.jpg"/><iframe class="embedded-video" src="http://www.youtube.com/embed/%s" allowfullscreen></iframe>', $query['v'], $query['v']);
	}
	
	//links
	return sprintf('<a href="%1$s">%1$s</a>', $arr[0]);
}

$str = preg_replace_callback('#(?:https?://\S+)|(?:www.\S+)|(?:\S+\.\S+)#', 'converterLinksEmVideos', $str);

echo $str;