PHP warnings on invalid domain about lightopenid HOT 5 CLOSED

I have thought about how to fix the problem, but have no idea so far.

I know of no method to check validity of the url without actually connecting to 
it, and therefore generating a warning.

There is checkdnsrr() function, but it only works for dns names (so for example 
"localhost" wouldn't work).

Suppressing the error with @ isn't a good solution either, because it will 
generate the error anyway (interfering with custom error handlers).

If you (or anyone else) have any idea how to do it, please tell me.

Sorry, I don't have a good idea.

The following code handles the case of invalid domains by using gethostbynamel 
which supports both "localhost" and ip-addresses. 

But if the domain exists and there is just no webserver, it will still cause a 
silent error.

--- lightopenid.php     27 Sep 2010 17:46:37 -0000      1.5
+++ lightopenid.php     27 Sep 2010 18:32:10 -0000
@@ -148,8 +148,16 @@
             );

             $url = $url . ($params ? '?' . $params : '');
-            $headers_tmp = get_headers ($url);
-            
+
+            # connecting to server
+            if (!$this->doesServerExist($url)) {
+                return null;
+            }
+            $headers_tmp = @get_headers($url);
+            if (!isset($headers_tmp)) {
+                return null;
+            }
+
             # Parsing headers.
             $headers = array();
             foreach($headers_tmp as $header) {
@@ -225,6 +233,9 @@
         for ($i = 0; $i < 5; $i ++) {
             if ($yadis) {
                 $headers = $this->request($url, 'HEAD');
+                if (!isset($headers)) {
+                    throw new ErrorException('No servers found!');
+                }

                 $next = false;
                     if (isset($headers['x-xrds-location'])) {
@@ -602,4 +613,24 @@
         }
         return $this->getSregAttributes();
     }
+
+    /**
+     * checks if the server specified in the url exists.
+     *
+     * @param $url url to check
+     * @return true, if the server exists; false otherwise
+     */
+    function doesServerExist($url)
+    {
+        if (strpos($url, '/') === false) {
+            $server = $url;
+        } else {
+            $server = @parse_url($url, PHP_URL_HOST);
+        }
+        if ($server === false) {
+            return false;
+        }
+        $ip = gethostbynamel($server);
+        return ($ip !== false);
+    }
 }




phpunit:
<?php
require_once('lib/openid/lightopenid.php');

class LightOpenidTest extends PHPUnit_Framework_TestCase {

    public function testDoesServerExist() {
        $openid = new LightOpenID();
        $this->assertTrue($openid->doesServerExist("localhost"));
        $this->assertTrue($openid->doesServerExist("www.google.com"));
        $this->assertTrue($openid->doesServerExist("ip6-loopback"));
        $this->assertTrue($openid->doesServerExist("127.0.0.1"));
        $this->assertFalse($openid->doesServerExist("not.exists"));

        $this->assertTrue($openid->doesServerExist("http://me.yahoo.com"));
        $this->assertTrue($openid->doesServerExist("http://me.yahoo.com/"));
        $this->assertTrue($openid->doesServerExist("http://me.yahoo.com:80"));
        $this->assertTrue($openid->doesServerExist("http://me.yahoo.com:80/"));

        $this->assertFalse($openid->doesServerExist("http://not.exists"));
        $this->assertFalse($openid->doesServerExist("http://not.exists/"));
        $this->assertFalse($openid->doesServerExist("http://not.exists:80/"));
    }
}


PS: Thanks a lot for your fixes and providing lightopenid in the first place.

Thanks! I'll include the fix.

However, throwing an error after the first HEAD fails isn't correct behavior. 

From section 7.3 of the spec:
If the Yadis protocol fails [realized mostly by a HEAD request] and no valid 
XRDS document is retrieved, or no Service Elements are found in the XRDS 
document, the URL is retrieved and HTML-Based discovery SHALL be attempted.

And anyway, $headers would be set and equal to null, so that isset($headers) == 
true, and empty($headers) == true.

I would however throw an error if the server isn't found, because further 
discovery is impossible.

Ok, it's commited now, with some changes and unrelated bugfixes.

Also, I'm sure that you will test it, so please tell me if you find that 
everything works, so I can upload the current version as lightopenid-0.3.

I successfully tested it with myopenid.com, delegation to myopenid.com, google 
and yahoo. And there are no more php warning on invalid domains.

Thanks a lot.