Script to download and extract zip files returns errors

Question

Hey everyone, I have written a script that downloads a zip file from a remote source, and then is supposed to extract the zip file to a directory. Below is the script:

    <?php
        $url = "http://example.com/some_file.zip";
        download($url,'file.zip');

        function download($url,$file_name = NULL){
          if($file_name == NULL){ $file_name = basename($url);}

          $url_stuff = parse_url($url);
          $port = isset($url_stuff['port']) ? $url_stuff['port'] : 80;

          $fp = fsockopen($url_stuff['host'], $port);
          if(!$fp){ return false;}

          $query  = 'GET ' . $url_stuff['path'] . " HTTP/1.0\n";
          $query .= 'Host: ' . $url_stuff['host'];
          $query .= "\n\n";

          fwrite($fp, $query);

          while ($tmp = fread($fp, 8192))   {
            $buffer .= $tmp;
          }

          preg_match('/Content-Length: ([0-9]+)/', $buffer, $parts);
          $file_binary = substr($buffer, - $parts[1]);
          if($file_name == NULL){
            $temp = explode(".",$url);
            $file_name = $temp[count($temp)-1];
          }
          if(!file_exists("packages")){ mkdir("packages", 0755);}
          $file_open = fopen("packages/" . $file_name,'w');
          if(!$file_open){ return false;}
          fwrite($file_open,$file_binary);

          $zip = zip_open(realpath("packages")."/".$file_name);
          if ($zip) {
            while ($zip_entry = zip_read($zip)) {
              $fp = fopen("some_dir/".zip_entry_name($zip_entry), "w");
              if(zip_entry_open($zip, $zip_entry, "r")) {
                $buf = zip_entry_read($zip_entry, zip_entry_filesize($zip_entry));
                fwrite($fp,"$buf");
                zip_entry_close($zip_entry);
                fclose($fp);
              }
            }
            zip_close($zip);
          }
          fclose($file_open);
          return true;
        }
   ?>

The issue that I have is that while the downloading of the remote file works flawlessly, I can't seem to extract it. The zip_read() and zip_close() return errors saying that it "expects parameter 1 to be resource, integer given...", which I have found means that the zip_open() was unable to extract and is returning an error code, which I have found to be "19" meaning "Zip File Function error: Not a zip archive". However, I know the file I am downloading is, in fact, a zip file. Can anyone explain this odd behavior and provide a fix? It would be much appreciated!

Answer 1

Quoting php.net: "zip_open() ... Returns a resource handle for later use with zip_read() and zip_close() or returns the number of error if filename does not exist or in case of other error."

This means you cannot test if ($zip) like that. Try

if ( is_resource($zip) ) {
    // stuff
} else {
    print "Zip_open() returned error $zip\n";
}

edit: Apart from that, you need to cut the response in 2 parts properly. You are relying heavily on the Content-Length parameter. You don't check if the preg_match actually matched. A lot of things can go wrong and you should check those things. Try splitting the content on the first empty line (explode on \r\n\r\n or something like that)

Besides the fread() loop should check for feof(), since you would stop reading now if for some reason you would encounter an empty read. Copy&paste from php.net:

while (!feof($handle)) {
    $contents .= fread($handle, 8192);
}

But we can go on and on here. Three main points have to be made:

• read the fantastic manual (php.net)
• check return values
• don't assume you know things you don't

those are related: you must lookup the manual to see what return values you might encounter.