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This interesting article found on Zend.com will explain to you how to create ZIP files on the fly using PHP.

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Ever wondered how you could create ZIP files on the fly? In this article, which I found on Zend.com, you’ll be able to. The original version can be found here: http://www.zend.com/zend/spotlight/creating-zip-files2.php

? php

/*

Zip file creation class
makes zip files on the fly…

use the functions add_dir() and add_file() to build the zip file;
see example code below

by Eric Mueller
http://www.themepark.com

v1.1 9-20-01
– added comments to example

v1.0 2-5-01

initial version with:
– class appearance
– add_file() and file() methods
– gzcompress() output hacking
by Denis O.Philippov, webmaster@atlant.ru, http://www.atlant.ru

*/

// official ZIP file format: http://www. // pkware.com/appnote.txt

class zipfile
{

var $datasec = array(); // array to store compressed data
var $ctrl_dir = array(); // central directory
var $eof_ctrl_dir = “\x50\x4b\x05\x06\x00\x00\x00\x00″; //end of Central directory record
var $old_offset = 0;

function add_dir($name)

// adds “directory” to archive – do this before putting any files in directory!
// $name – name of directory… like this: “path/”
// …then you can add files using add_file with names like “path/file.txt”
{
$name = str_replace(”\\”, “/”, $name);

$fr = “\x50\x4b\x03\x04″;
$fr .= “\x0a\x00″; // ver needed to extract
$fr .= “\x00\x00″; // gen purpose bit flag
$fr .= “\x00\x00″; // compression method
$fr .= “\x00\x00\x00\x00″; // last mod time and date

$fr .= pack(”V”,0); // crc32
$fr .= pack(”V”,0); //compressed filesize
$fr .= pack(”V”,0); //uncompressed filesize
$fr .= pack(”v”, strlen($name) ); //length of pathname
$fr .= pack(”v”, 0 ); //extra field length
$fr .= $name;
// end of “local file header” segment

// no “file data” segment for path

// “data descriptor” segment (optional but necessary if archive is not served as file)
$fr .= pack(”V”,$crc); //crc32
$fr .= pack(”V”,$c_len); //compressed filesize
$fr .= pack(”V”,$unc_len); //uncompressed filesize

// add this entry to array
$this -> datasec[] = $fr;

$new_offset = strlen(implode(”", $this->datasec));

// ext. file attributes mirrors MS-DOS directory attr byte, detailed
// at http://support.microsoft.com/support/kb/articles/Q125/0/19.asp

// now add to central record
$cdrec = “\x50\x4b\x01\x02″;
$cdrec .=”\x00\x00″; // version made by
$cdrec .=”\x0a\x00″; // version needed to extract
$cdrec .=”\x00\x00″; // gen purpose bit flag
$cdrec .=”\x00\x00″; // compression method
$cdrec .=”\x00\x00\x00\x00″; // last mod time & date
$cdrec .= pack(”V”,0); // crc32
$cdrec .= pack(”V”,0); //compressed filesize
$cdrec .= pack(”V”,0); //uncompressed filesize
$cdrec .= pack(”v”, strlen($name) ); //length of filename
$cdrec .= pack(”v”, 0 ); //extra field length
$cdrec .= pack(”v”, 0 ); //file comment length
$cdrec .= pack(”v”, 0 ); //disk number start
$cdrec .= pack(”v”, 0 ); //internal file attributes
$ext = “\x00\x00\x10\x00″;
$ext = “\xff\xff\xff\xff”;
$cdrec .= pack(”V”, 16 ); //external file attributes – ‘directory’ bit set

$cdrec .= pack(”V”, $this -> old_offset ); //relative offset of local header
$this -> old_offset = $new_offset;

$cdrec .= $name;
// optional extra field, file comment goes here
// save to array
$this -> ctrl_dir[] = $cdrec;

}

function add_file($data, $name)

// adds “file” to archive
// $data – file contents
// $name – name of file in archive. Add path if your want

{
$name = str_replace(”\\”, “/”, $name);
//$name = str_replace(”\\”, “\\\\”, $name);

$fr = “\x50\x4b\x03\x04″;
$fr .= “\x14\x00″; // ver needed to extract
$fr .= “\x00\x00″; // gen purpose bit flag
$fr .= “\x08\x00″; // compression method
$fr .= “\x00\x00\x00\x00″; // last mod time and date

$unc_len = strlen($data);
$crc = crc32($data);
$zdata = gzcompress($data);
$zdata = substr( substr($zdata, 0, strlen($zdata) – 4), 2); // fix crc bug
$c_len = strlen($zdata);
$fr .= pack(”V”,$crc); // crc32
$fr .= pack(”V”,$c_len); //compressed filesize
$fr .= pack(”V”,$unc_len); //uncompressed filesize
$fr .= pack(”v”, strlen($name) ); //length of filename
$fr .= pack(”v”, 0 ); //extra field length
$fr .= $name;
// end of “local file header” segment

// “file data” segment
$fr .= $zdata;

// “data descriptor” segment (optional but necessary if archive is not served as file)
$fr .= pack(”V”,$crc); //crc32
$fr .= pack(”V”,$c_len); //compressed filesize
$fr .= pack(”V”,$unc_len); //uncompressed filesize

// add this entry to array
$this -> datasec[] = $fr;

$new_offset = strlen(implode(”", $this->datasec));

// now add to central directory record
$cdrec = “\x50\x4b\x01\x02″;
$cdrec .=”\x00\x00″; // version made by
$cdrec .=”\x14\x00″; // version needed to extract
$cdrec .=”\x00\x00″; // gen purpose bit flag
$cdrec .=”\x08\x00″; // compression method
$cdrec .=”\x00\x00\x00\x00″; // last mod time & date
$cdrec .= pack(”V”,$crc); // crc32
$cdrec .= pack(”V”,$c_len); //compressed filesize
$cdrec .= pack(”V”,$unc_len); //uncompressed filesize
$cdrec .= pack(”v”, strlen($name) ); //length of filename
$cdrec .= pack(”v”, 0 ); //extra field length
$cdrec .= pack(”v”, 0 ); //file comment length
$cdrec .= pack(”v”, 0 ); //disk number start
$cdrec .= pack(”v”, 0 ); //internal file attributes
$cdrec .= pack(”V”, 32 ); //external file attributes – ‘archive’ bit set

$cdrec .= pack(”V”, $this -> old_offset ); //relative offset of local header
// &n // bsp; echo “old offset is “.$this->old_offset.”, new offset is $new_offset
“;
$this -> old_offset = $new_offset;

$cdrec .= $name;
// optional extra field, file comment goes here
// save to central directory
$this -> ctrl_dir[] = $cdrec;
}

function file() { // dump out file
$data = implode(”", $this -> datasec);
$ctrldir = implode(”", $this -> ctrl_dir);

return
$data.
$ctrldir.
$this -> eof_ctrl_dir.
pack(”v”, sizeof($this -> ctrl_dir)). // total # of entries “on this disk”
pack(”v”, sizeof($this -> ctrl_dir)). // total # of entries overall
pack(”V”, strlen($ctrldir)). // size of central dir
pack(”V”, strlen($data)). // offset to start of central dir
“\x00\x00″; // .zip file comment length
}
}

?

Example Usage of the Class

? php

$zipfile = new zipfile();

// add the subdirectory … important!
$zipfile -> add_dir(”dir/”);

// add the binary data stored in the string ‘filedata’
$filedata = “(read your file into $filedata)”;
$zipfile -> add_file($filedata, “dir/file.txt”);

// the next three lines force an immediate download of the zip file:
header(”Content-type: application/octet-stream”);
header(”Content-disposition: attachment; filename=test.zip”);
echo $zipfile -> file();

// OR instead of doing that, you can write out the file to the loca disk like this:
$filename = “output.zip”;
$fd = fopen ($filename, “wb”);
$out = fwrite ($fd, $zipfile -> file());
fclose ($fd);

// then offer it to the user to download:
Click here to download the new zip file.

?

Posted on August 13th, 2008 by Denie
Filed under: Scripting