[RESOLVED] Checking the existance of files on another server?

[kerunt]

Hi all,

I need to write a PHP script to check the existance of other (known) files on another web-host. This script will check to see if they exist, if they do, it will forward the user to that site. If the files do not exist, it will forward the user to a mirror.

How can I do this?
I was told to use the "ftp extension"?

I have moderate knowlege of PHP, but I haven't heard of or used the ftp extension...

Any tips or solutions?

Thanks!

[bpat1434]

Read the manual first, then come ask questions:
[man]ftp[/man]

~Brett

[Babbs]

bpat1434 - I understand that kerunt specifically mentioned FTP, but my question is if the file isn't on a FTP server (or on one that you can not login to), which function should we look to?

[bpat1434]

you should look to put those files in an FTP-able area....

I don't know if PHP can actually do anything remotely to a server. It's possible to execute a shell script, but I don't know about on a remote server. That's a major security issue.

[bokehman]

bpat1434 wrote:

Read the manual first, then come ask questions

Why bother with these "read the manual" answers? Why not just not post at all? All you are doing is watering down what could be a useful thread with drival.

If you want to check for existence of a file on a remote server but not download it you could use the following function:

function http_file_exists($url, $followRedirects = true)
{
   $url_parsed = parse_url($url);
   if (!@$url_parsed['scheme']) $url_parsed = parse_url('http://'.$url);
   extract($url_parsed);
   if(!@$port) $port = 80;
   if(!@$path) $path = '/';
   if(@$query) $path .= '?'.$query;
   $out = "HEAD $path HTTP/1.0\r\n";
   $out .= "Host: $host\r\n";
   $out .= "Connection: Close\r\n\r\n";
   if(!$fp = @fsockopen($host, $port, $es, $en, 5)){
	   return false;
   }
   fwrite($fp, $out);
   while (!feof($fp)) {
	   $s = fgets($fp, 128);
	   if(($followRedirects) && (preg_match('/^Location:/i', $s) != false)){
		   fclose($fp);
	       return http_file_exists(trim(preg_replace("/Location:/i", "", $s)));
       }
       if(preg_match('/^HTTP(.*?)200/i', $s)){
	       fclose($fp);
	       return true;
       }
   }
   fclose($fp);
   return false;
}

[bpat1434]

Bokehman:
Give a man a fish, feed him for a day. Teach a man to fish, feed him for life.
~ Chinese Proverb.

If you get them to learn how to read the manual, and use it, then the user will have less "new" questions and their later questions will be more intricate and require some type of intervention.

I'm not saying what you did was wrong. But most of the higher-post-count posters here believe that users should know about the manual and use it. As with this question, most questions can be answered with a simple manual search. It's like getting a new Ashton-Martin, and then not reading the manual on how to start it and breaking your car. If it's there as a resource, use it. That's all we are saying.

For the more enlightened user, they'll say "Oh, didn't know where to look for the manual" or "I've already read that, any other hints/suggestions?". I didn't see that in the first post, which tells me two things:
1.) They didn't read the manual
2.) They didn't search the manual for the functions(s) they needed.

The question was about FTP functions: I pointed him to the manual as everything I'd say, would be in the manual. They then asked if a non-FTP area on the server can be searched. The answer was that I don't think it can, because of security.

Your function checks to see if the HTTP file is there. While it can be adapted, what if it's in a non-HTML area of the site? Say above the public_html or www folders? Like how WHMAutoPilot uses a folder outside of the document root. Your file wouldn't search those areas. So your code isn't a "solution" to this.

And I notice you only have 25 posts. When you get to a point where you answer more and more of the same question, you'll realize how invaluable the manual is and point people there. I help plenty of people out with code.... but in this instance, a manual reference was needed as all the FTP functions would take too long to document here.

[bradgrafelman]

I'm not trying to start a flamefest (and hopefully not stepping into one), but...

Nice quote of the Chinese proverb, bpat. It was on the tip of my tongue until I read your post, heh.

Generally, I try to help the person as well, instead of spoonfeeding them the solution. Would it be easier and quicker for me to simply type up a quick little function/block of code for them? Most likely... yes. Are they going to learn anything from that? Well, if they were die-hard programmers, yes, they would look at it piece-by-piece and follow what I was doing. Otherwise, they would simply be glad to have found a solution, plop it into their scripts, and away they go, nothing gained.

Referencing manuals, giving hints/suggestions as to what function/class/method/etc. to use, and so on can be a little frustrating, but so much more beneficial.

[bokehman]

The manual contains 5200 pages so telling the poster to read the manual and then pointing them to the completely WRONG and IRRELEVANT function for the job was certainly bogus. At least try to furnish people with relevant information.

[bpat1434]

How was FTP the wrong function? Let's see this?

How can I do this?
I was told to use the "ftp extension"?

I linked to the FTP function... sounds reasonable enough.... Myth 1 debunked!!

Would like to try and degrade me further?

Liek I said, YOUR function checks only if the file is UNDER the web-visible directory. What about above public_html? What about those? You can't get there from the web. You have to use FTP. So the FTP function (and manual pages relating to them) were the correct resource to link.

Please, think before you post.

[kerunt]

Thanks for the help and suggestions guys. I will check out the above code and read up on FTP functions first thing tomorrow morning.

bpat1434, I completely understand why you said "read the manual", I've felt exactly the same way as you before. The thing is that when I posted this thread, I had absolutely no idea how to go about the problem, and "ftp extension" is all I got when I asked for suggestions on a PHP irc channel. It really didn't mean much to me at the time, and I felt I needed either a more in depth explanation of what exactly "php extension" was, or another suggestion. Not really an excuse (I should have read the manual), but that's what happened.

Also, the higher-post count users know about the manual and feel other's should too because they are more experienced (thus the larger post count) and more familiar with it. To be honest, I look at the manual once in a while, but I find better discussions and solutions on various forums.

My files will be in public_html, they will be accessible via the web.

Babbs, you bring up a valid point about the possibility of files not being on an FTP server. However, in my case, the files will be FTP accessible.

bokehman, I understand where you're coming from too, but in this case I really should have read the manual, and seeing that I had 1 posts, I'm sure that more-than encouraged the RTFM reply 😉.

Thanks for the code! I will try it tomorrow morning and see if it works like I need it to.

bradgrafelman, I agree with how you approach problems. An example and an explanation is usualy the best learning material. In either case, I always look at and try to understand the code before using it.

Again, thanks for all the input!

[bokehman]

bpat1434 wrote:

How was FTP the wrong function? Let's see this?

I linked to the FTP function... sounds reasonable enough.... Myth 1 debunked!!

Would like to try and degrade me further?

Please, think before you post.

My answer was based on the fact that the question was "how do I check files on another web-host". A web host does not serve files via ftp or files that are ascendant to root. Therefore in my opinion HTTP is the only correct protocol to use in this instance.

[bpat1434]

Of course, a simple [man]file_get_contents[/man](URL TO FILE) would do the same thing. so your entire code could be:

<?php
$url = 'http://www.domain.com/some/file.php';

if(!$contents = file_get_contents($url))
{
    // Uh oh, error
}
else
{
    // no error
}
?>

But that's beside the point. My point was, they specifically asked about the FTP issue. The manual can offer more documentation than I would care to explain. And it wasn't really a RTFM, it was Read the manual, then come ask questions.

And web-hosts allow you to keep files/folders outside of the document root. And what about .htaccess protected files/folders? FTP could see them, HTTP can't.

You were right, and I was right. Some cases, the HTTP is better, some cases FTP. It's a situational call.

End of discussion.

[bokehman]

bpat1434 wrote:

Of course, a simple [man]file_get_contents[/man](URL TO FILE) would do the same thing.

Not quite! It will download the whole file just to check it exists (if it was 100 megabytes the script would time out).

[madwormer2]

Plus you'd just end up getting the error 404 document if the file didn't exist.

And talking of proverbs and flames...

Build a man a fire, you keep him warm for the night. Set a man on fire, and you keep him warm for the rest of his life.

[MarkR]

You can use fopen() with a stream context to instruct it to do a HEAD request rather than a GET; this will allow you to check for the file's existence without downloading the entire contents.

Alternatively, you could use file_get_contents() anyway, and specify a value for the optional maxlen parameter, in which case it would only get part of the file.

Mark

[kerunt]

bokehman, the code you posted works like a charm, now I'm going to dig in and see if I understand it all 🙂.

Thanks to everyone!

[Weedpacket]

MarkR wrote:

You can use fopen() with a stream context to instruct it to do a HEAD request rather than a GET;

Assuming you're using PHP5; if you're still using PHP4 you don't have such control.