Checking link validitiy

Anon

I have a database with links to external sites. But when someone clicks on a link to spawn that site I check to the site to see if it is a valid link because I dont want to show a user a File not found link, because someone elses server is down or the link has been removed.
So this is what I do

$output=implode("\n",file($output));
if ((strlen($output)>0)&&(strpos($output,"HTTP 404")<1))
{
//goto the link
}
else
{
//redirect to my own custom error.
}
So right now its loading the contents of that entire site into a variable and then parsing through it to see if its ok or not. It works for most cases but probably not all.

I was wondering if anyone knows a better way to check if a link is valid before going to it.

Thanks

pnoeric

Ryan - you could fsockopen the remote HTTP server and send a HEAD request. The HTTP 1.1 protocol document says, in fact, "The HEAD method is identical to GET except that the server MUST NOT return a message-body in the response. The metainformation contained in the HTTP headers in response to a HEAD request SHOULD be identical to the information sent in response to a GET request. This method can be used for obtaining metainformation about the entity implied by the request without transferring the entity-body itself. This method is often used for testing hypertext links for validity, accessibility, and recent modification."

best,
Eric

lucidfx

Alright I tried both fsockopen and fopen

fsockopen seems better since it doesn't get the entire site, but it doesn't work for sites other then the domain, like if its has /andfilenames.htm or whatever it returns 0. fopen works for what i need to do but i dont want to grab all the file just to check if its their if i dont have to.

any more advice 🙂

pnoeric

Hey Ryan... hmmm fsockopen will only open a domain. After you do that, you need to parse out the rest of the URL into the "HEAD" request.

If you are after yahoo.com/dir/blah.htm, ou should fsockopen yahoo.com
then send the HTTP headers with the line HEAD /dir/blah.htm, and look at the result code from that. Experiment a little bit with this one :-)

best,
Eric