i'd say the best place to learn php is the http://php.net but to each his own...
but nice idea and nice site. the best part is that everything is functional and works
few pointers about the site imo...
better use dereferrer services http://dereferer.org/start.asp so that the site you're linking to does not know where the request came from.
if you don't use a dereferrer then in case, a site where the actual resource is hosted, is taken down, then the site records will show that your website was used to share the content. but if you did then you'd be safe (to certain extent).
- videos ... youtube support would be great