hairyfairy just check strpos($str,'://')
if it's >= 1 (which means there's at least a 1-byte/char protocol), you're good
granted, you'll be riddled with false positives, but hey, IT WORKS
it will be "something" that will have the "STRUCTURE of an URL"
oh wait, mailto: urls !
just check strpos($str,':')
oh wait, protocol-relative URLs !