Question

Before I dive into writing a validator to check if a URL is actually pointing to an RSS feed, I did a bit of searching for some validators that may exist out there but had little luck with any reliable ones.

I just wanted to ask the community if any of you know of an RSS validator by URL?

If I were to write my own, what do you suggest?

I was thinking of just checking for the first instance of a line of text and making sure it defines <?xml version="1.0" encoding="UTF-8"?> and then perhaps checking that the next item is an <rss> node.

What are your thoughts here? Could there ever be a case where a feed may not follow the syntax stated above?

Also note, one method I attempted to use was the following:

$valid = true;

try{
    $content = file_get_contents($feed);
    if (!simplexml_load_string($content)){
        $valid = false;
    }
} catch (Exception $e){
    $valid = false;
}

Unfortunately it seems that I cannot suppress warnings (error_reporting(0) is not working..) so the just spams me with warnings.

---

SOLUTION

For anyone that is interested, I used the W3C Validator API

$url = "http://feed_url.com";
$validator = "http://validator.w3.org/feed/check.cgi";
$validator .= "?url=".$url;
$validator .= "&output=soap12";

$response = file_get_contents($validator);
$a = strpos($response, '<m:validity>', 0)+12; 
$b = strpos($response, '</m:validity>', $a); 
$result = substr($response, $a, $b-$a); 
echo $result;

This will return true or false accordingly.

Answer 1

The W3C Feed Validation Service offers a SOAP interface. From the About page:

Is there a Web Service with a public API for this service?

Yes, there is a SOAP interface, accessible by using the query
parameter output=”soap12″ on top of a regular query. The SOAP 1.2 Web
Service API documentation has more details.