title: Is FILTER_VALIDATE_URL being too strict?
body: <p>In PHP, <code>filter_var('www.example.com', FILTER_VALIDATE_URL)</code> returns <code>false</code>. Is this correct? Isn't <code>www.example.com</code> a valid URL, or protocols (http://, ftp://, etc.) need to be explicitly stated in the URL to be formally correct?</p>