Zip en download folder

<?php
/**
 * This class creates a ZIP file, but in a string, so it can be streamed to the 
 * browser without first having to be saved on disk.
 * This class is based on the zipfile class in zip.lib.php which can be found in
 * the phpmyadmin directory. Some minor changes have been made to get it to work
 * though.
 */
class Zip_Streamer_Class{
  
  /**
   * Array to store compressed data
   * @var array 
   */
  private $datasec;

  /**
   * Central directory
   * @var array 
   */ 
  private $ctrl_dir;

  /**
   * End of central directory record
   * @var string
   */
  private $eof_ctrl_dir;

  /**
   * Last offset position
   * @var int 
   */
  private $old_offset;
  
/* -- constructor ----------------------------------------------------------- */
  
  /**
   * Constructor which initializes the properties 
   */
  public function __construct(){
    $this->resetProperties();
  }
  
/* -- private methods ------------------------------------------------------- */  

  /**
   * 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  int $unixtime
   * @return int the current date in a four byte DOS format
   */
  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;
    } 

    return (($timearray['year'] - 1980) << 25) | ($timearray['mon'] << 21) | ($timearray['mday'] << 16) |
            ($timearray['hours'] << 11) | ($timearray['minutes'] << 5) | ($timearray['seconds'] >> 1);
  } 
  
  /**
   * Fully convert the time from unix timestamp.
   * @param int $time
   * @return string 
   */
  private function convertTime( $time ){
    $dtime    = dechex($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 . '";');
    
    return $hexdtime;
  }
  
  /**
   * Reset all properties to their initial value. This will effectively clear
   * the contents of the zip. 
   */
  private function resetProperties(){
    $this->datasec = array();
    $this->ctrl_dir = array();
    $this->eof_ctrl_dir = "\x50\x4b\x05\x06\x00\x00\x00\x00";
    $this->old_offset = 0;
  }

/* -- public methods -------------------------------------------------------- */ 
  
  /**
   * Adds "file" to archive. The file is given with the name that it should get
   * in the archive and the contents of the file ($data). $time is the current 
   * timestamp (can be ommited)
   * @param string $data
   * @param string $name
   * @param int $time 
   */
  public function addFile( $data, $name, $time = 0 ){
    $name     = str_replace('\\', '/', $name);

    $hexdtime = $this->convertTime( $time );
    /*$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);
    $zdata   = substr(substr($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;

    // "file data" segment
    $fr .= $zdata;

    // "data descriptor" segment (optional but necessary if archive is not
    // served as file)
    // nijel(2004-10-19): this seems not to be needed at all and causes
    // problems in some cases (bug #1037737)
    // EH: doesn't work without this part....
    $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;

    // 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
    $this->old_offset += strlen($fr);

    $cdrec .= $name;

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

  /**
    * Dumps out file
    * @return string
    */
  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
  } 
  
  /**
   * Empty all content that is added to the zip already. This will reset all
   * values and clears everything. 
   */
  public function emptyZip(){
    $this->resetProperties();
  }
}
?>