Hi,

I am using code available on http://www.forosdelweb.com/f18/zip-lib-php-archivo-zip-vacio-431133/ for creating zip file.

First file-zip.lib.php

<?php
/* $Id: zip.lib.php,v 1.1 2004/02/14 15:21:18 anoncvs_tusedb Exp $ */
// vim: expandtab sw=4 ts=4 sts=4:


/**
* Zip file creation class.
* Makes zip files.
*
* Last Modification and Extension By :
*
*  Hasin Hayder
*  HomePage : www.hasinme.info
*  Email : [email protected]
*  IDE : PHP Designer 2005
*
*
* Originally Based on :
*
*  http://www.zend.com/codex.php?id=535&single=1
*  By Eric Mueller <[email protected]>
*
*  http://www.zend.com/codex.php?id=470&single=1
*  by Denis125 <[email protected]>
*
*  a patch from Peter Listiak <[email protected]> for last modified
*  date and time of the compressed file
*
* Official ZIP file format: http://www.pkware.com/appnote.txt
*
* @access  public
*/
class zipfile
 {
/**
 * Array to store compressed data
 *
 * @var  array    $datasec
 */
var $datasec      = array();

/**
 * Central directory
 *
 * @var  array    $ctrl_dir
 */
var $ctrl_dir     = array();

/**
 * End of central directory record
 *
 * @var  string   $eof_ctrl_dir
 */
var $eof_ctrl_dir = "\x50\x4b\x05\x06\x00\x00\x00\x00";

/**
 * Last offset position
 *
 * @var  integer  $old_offset
 */
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);
    $zdata   = substr(substr($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)
    $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;
} // 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


/**
 * A Wrapper of original addFile Function
 *
 * Created By Hasin Hayder at 29th Jan, 1:29 AM
 *
 * @param array An Array of files with relative/absolute path to be added in Zip File
 *
 * @access public
 */
function addFiles($files /*Only Pass Array*/)
{
    foreach($files as $file)
    {
    if (is_file($file)) //directory check
    {
        $data = implode("",file($file));
                $this->addFile($data,$file);                    
            }
    }
}

/**
 * A Wrapper of original file Function
 *
 * Created By Hasin Hayder at 29th Jan, 1:29 AM
 *
 * @param string Output file name
 *
 * @access public
 */
function output($file)    {
    $fp=fopen($file,"w");
    fwrite($fp,$this->file());
    fclose($fp);
}



} // end of the 'zipfile' class
?> 

My second file newzip.php

<?
include("zip.lib.php");
$ziper = new zipfile();
$ziper->addFiles(array("index.htm"));  //array of files 
 //  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 $ziper -> file(); 
?>

I am getting this warning while executing newzip.php

Warning: Cannot modify header information - headers already sent by (output started at E:\xampp\htdocs\demo\zip.lib.php:233) in E:\xampp\htdocs\demo\newzip.php on line 6

I am unable to figure out the reason for the same.

Please help me on this.

Thanks