Zip files on php without ZIP library

php_zip.inc

<?php
// $Id$
/**
 * @file
 * Zip class for servers without ziplib.
 */

class PHPZip {
  function Zip($dir, $zipfilename) {
      if (@function_exists('gzcompress')) { 
      $curdir = getcwd();
      if (is_array($dir)) {
          $filelist = $dir;
      }
      else {
        $filelist = $this->GetFileList($dir);
      }
      
      if ((!empty($dir))&&(!is_array($dir))&&(file_exists($dir))) {
        chdir($dir);
      }
      else {
        chdir($curdir);
      }

      if (count($filelist)>0) {
        foreach ($filelist as $filename) {
          if (is_file($filename)) {
            $fd = fopen($filename, "r");
            $content = fread($fd, filesize($filename));
            fclose($fd);

            if (is_array($dir)) $filename = basename($filename);
            $this->addFile($content, $filename);
          }
        }
        $out = $this->file();

        chdir($curdir);
        $fp = fopen($zipfilename, "w");
        fwrite($fp, $out, strlen($out));
        fclose($fp);
      }
      return 1;
    } 
    else return 0;
  }

  function GetFileList($dir) {
    if (file_exists($dir)) {
      $args = func_get_args();
      $pref = $args[1];
    
      $dh = opendir($dir);
      while ($files = readdir($dh)) {
        if (($files!= ".") && ($files != "..")) {
          if (is_dir($dir . $files)) {
            $curdir = getcwd();
            chdir($dir . $files);
            $file = array_merge($file, $this->GetFileList("", "$pref$files/"));
            chdir($curdir);
          }
          else $file[] = $pref . $files;
        }
      }
      closedir($dh);
    }
    return $file;
  }

    var $datasec      = array();
    var $ctrl_dir     = array();
    var $eof_ctrl_dir = "\x50\x4b\x05\x06\x00\x00\x00\x00";
    var $old_offset   = 0;

    /**
     * Converts an Unix timestamp to a four byte DOS date and time format (date
     * in high two bytes, time in low two bytes allowing magnitude comparison).
     *
     * @param  integer  the current Unix timestamp
     *
     * @return integer  the current date in a four byte DOS format
     *
     * @access private
     */
    function unix2DosTime($unixtime = 0) {
        $timearray = ($unixtime == 0) ? getdate() : getdate($unixtime);

        if ($timearray['year'] < 1980) {
          $timearray['year']    = 1980;
          $timearray['mon']     = 1;
          $timearray['mday']    = 1;
          $timearray['hours']   = 0;
          $timearray['minutes'] = 0;
          $timearray['seconds'] = 0;
        } // end if

        return (($timearray['year'] - 1980) << 25) | ($timearray['mon'] << 21) | ($timearray['mday'] << 16) |
                ($timearray['hours'] << 11) | ($timearray['minutes'] << 5) | ($timearray['seconds'] >> 1);
    } // end of the 'unix2DosTime()' method


    /**
     * Adds "file" to archive
     *
     * @param  string   file contents
     * @param  string   name of the file in the archive (may contains the path)
     * @param  integer  the current timestamp
     *
     * @access public
     */
    function addFile($data, $name, $time = 0) {
        $name     = str_replace('\\', '/', $name);

        $dtime    = dechex($this->unix2DosTime($time));
        $hexdtime = '\x'. $dtime[6] . $dtime[7]
                  .'\x'. $dtime[4] . $dtime[5]
                  .'\x'. $dtime[2] . $dtime[3]
                  .'\x'. $dtime[0] . $dtime[1];
        eval('$hexdtime = "'. $hexdtime .'";');

        $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   .= $hexdtime;             // last mod time and date

        // "local file header" segment
        $unc_len = strlen($data);
        $crc     = crc32($data);
        $zdata   = gzcompress($data);
        $c_len   = strlen($zdata);
        $zdata   = substr(substr($zdata, 0, strlen($zdata) - 4), 2); // fix crc bug
        $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;

        // "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 .= $hexdtime;                 // 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
        $this->old_offset = $new_offset;

        $cdrec .= $name;

        // optional extra field, file comment goes here
        // save to central directory
        $this->ctrl_dir[] = $cdrec;
    } // end of the 'addFile()' method


    /**
     * Dumps out file
     *
     * @return  string  the zipped file
     *
     * @access public
     */
    function 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
    } // end of the 'file()' method
}

php_zip_usage.php

<?php
//Usage
$z = new PHPZip();

$files_list = scandir($file_path);

//add the files
foreach ($files_list as $file_to_zip) {
  //scandir list "." and ".." so we need to skip them
  if ($file_to_zip != '.' && $file_to_zip != '..') {
    $content = file_get_contents($file_path . $file_to_zip);
    $z->addFile($content, $file_to_zip);
  }
}
$out = $z->file();

$fp = fopen($zip_file, "w");
fwrite($fp, $out, strlen($out));
fclose($fp);
?>