Youtube regex help

[dr.pepper]

Ive got a textarea where a user can enter as much text as they wish as well as multiple youtube videos. I would like them to be able to simply enter the url i.e http://www.youtube.com/watch?v=12345 for example and this will then be embedded onto the page.

 

I currently have it working if they enter a tag around the url e.g [youtube:http://www.youtube.com/watch?v=1234]  however I am trying to do it without the tags so that it is easier for them.

 

Here is my code, does anyone know how I can do it without the tags?

 

$body = str_replace("http://www.youtube.com/watch?v=", "http://www.youtube.com/v/", $body);
	  	
return preg_replace('/\[youtube:([^\]]+?)\]/', '<object width="460" height="340"><param name="movie" value="\\1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="\\1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="460" height="340"></embed></object>', $body);

 

Thanks!