Question

I have a random url, set as a string in PHP, Example:

$u='http://www.google.com/feedtest/something';

I am using simpleXML to get the feed from $u

How would you identify if the url is a feed (RSS,XML, ..) before downloading it with simpleXML?

Answer 1

You should be able to use get_headers() (see man page):

$url = 'http://www.example.com';
print_r(get_headers($url, 1));

Would give you back the following printout:

Array
(
    [0] => HTTP/1.1 200 OK
    [Date] => Sat, 29 May 2004 12:28:14 GMT
    [Server] => Apache/1.3.27 (Unix)  (Red-Hat/Linux)
    [Last-Modified] => Wed, 08 Jan 2003 23:11:55 GMT
    [ETag] => "3f80f-1b6-3e1cb03b"
    [Accept-Ranges] => bytes
    [Content-Length] => 438
    [Connection] => close
    [Content-Type] => text/html
)

So you could use something like:

$headers = get_headers($url, 1);

if($headers['Content-Type'] == 'application/rss+xml') {
    // read the file
}

As long as the server you are requesting these files from actually sends the correct response headers for RSS data.