Unzipping larger files with PHP

Question

I'm trying to unzip a 14MB archive with PHP with code like this:

    $zip = zip_open("c:\kosmas.zip");
    while ($zip_entry = zip_read($zip)) {
    $fp = fopen("c:/unzip/import.xml", "w");
    if (zip_entry_open($zip, $zip_entry, "r")) {
     $buf = zip_entry_read($zip_entry, zip_entry_filesize($zip_entry));
     fwrite($fp,"$buf");
     zip_entry_close($zip_entry);
     fclose($fp);
     break;
    }
   zip_close($zip);
  }

It fails on my localhost with 128MB memory limit with the classic "Allowed memory size of blablabla bytes exhausted". On the server, I've got 16MB limit, is there a better way to do this so that I could fit into this limit? I don't see why this has to allocate more than 128MB of memory. Thanks in advance.

Solution: I started reading the files in 10Kb chunks, problem solved with peak memory usage arnoud 1.5MB.

        $filename = 'c:\kosmas.zip';
        $archive = zip_open($filename);
        while($entry = zip_read($archive)){
            $size = zip_entry_filesize($entry);
            $name = zip_entry_name($entry);
            $unzipped = fopen('c:/unzip/'.$name,'wb');
            while($size > 0){
                $chunkSize = ($size > 10240) ? 10240 : $size;
                $size -= $chunkSize;
                $chunk = zip_entry_read($entry, $chunkSize);
                if($chunk !== false) fwrite($unzipped, $chunk);
            }

            fclose($unzipped);
        }

Answer 1

Why do you read the whole file at once?

 $buf = zip_entry_read($zip_entry, zip_entry_filesize($zip_entry));
 fwrite($fp,"$buf");

Try to read small chunks of it and writing them to a file.

Answer 2

Just because a zip is less than PHP's memory limit & perhaps the unzipped is as well, doesn't take account of PHP's overhead generally and more importantly the memory needed to actually unzip the file, which whilst I'm not expert with compression I'd expect may well be a lot more than the final unzipped size.

Answer 3

For a file of that size, perhaps it is better if you use shell_exec() instead:

shell_exec('unzip archive.zip -d /destination_path');

PHP must not be running in safe mode and you must have access to both shell_exec and unzip for this method to work.

Update:

Given that command line tools are not available, all I can think of is to create a script and send the file to a remote server where command line tools are available, extract the file and download the contents.

Answer 4

function my_unzip($full_pathname){

    $unzipped_content = '';
    $zd = gzopen($full_pathname, "r");

    while ($zip_file = gzread($zd, 10000000)){
        $unzipped_content.= $zip_file;
    }

    gzclose($zd);

    return $unzipped_content;

}