I am using this class to create zip

<?php  

// vim: expandtab sw=4 ts=4 sts=4:  



class zipfile  
{  

    var $datasec      = array();  


    var $ctrl_dir     = array();  


    var $eof_ctrl_dir = "\x50\x4b\x05\x06\x00\x00\x00\x00";  


    var $old_offset   = 0;  



    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  



    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  



    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  



    function addFiles($files )  
    {  
        foreach($files as $file)  
        {  
        if (is_file($file)) //directory check  
        {  
            $data = implode("",file($file));  
                    $this->addFile($data,$file);  
                }  
        }  
    }  


    function output($file)  
    {  
        $fp=fopen($file,"w");  
        fwrite($fp,$this->file());  
        fclose($fp);  
    }  



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

It creates zip file but when i try to open it on Mac os x snow leopard and windows 7, it doesnt open. on mac i had this error: Error 1: operation not permitted

Any idea ?

thanks