[PHP-ZIP] Creare Archivio ZIP "on-the-fly"

[marmz]

Ho trovato questa "semplice" libreria per creare ZIP:

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";                
        $cdrec .= "\x14\x00";                
        $cdrec .= "\x00\x00";                
        $cdrec .= "\x08\x00";                
        $cdrec .= $hexdtime;                 
        $cdrec .= pack('V', $crc);           
        $cdrec .= pack('V', $c_len);         
        $cdrec .= pack('V', $unc_len);       
        $cdrec .= pack('v', strlen($name) ); 
        $cdrec .= pack('v', 0 );             
        $cdrec .= pack('v', 0 );             
        $cdrec .= pack('v', 0 );             
        $cdrec .= pack('v', 0 );             
        $cdrec .= pack('V', 32 );            

        $cdrec .= pack('V', $this -> old_offset ); 
        $this -> old_offset += strlen($fr);

        $cdrec .= $name;
        $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)) . 
            pack('v', sizeof($this -> ctrl_dir)) .  
            pack('V', strlen($ctrldir)) .           
            pack('V', strlen($data)) .              
            "\x00\x00";                             
    } // end of the 'file()' method


} // end of the 'zipfile' class 

Più questa funzione che "aggiunge" una directory al mio archivio:

function add_dir($dir,$newzip)    # recursive adding of files to zip
{
static $no;
$no=$no+1;
if(($no>10)|| (strlen($newzip->file())>5000000)) die("Too many sub directories (>$no) or Total size > 5MB!<br>Try them by parts. [Some security measures!] ");
if($dh = opendir($dir)) 
  {
  $newzip->addFile("","$dir/",0);
  while (($file = readdir($dh)))  {$files[] = $file;}


  foreach($files as $file)
   {
    if($file!="."&&$file!=".."&&!is_dir("$dir/$file")&&is_readable("$dir/$file"))
    {
    $data=file_get_contents("$dir/$file");
    $newzip->addFile($data,"$dir/$file",0);
    }
   }
  foreach($files as $file)
   {
   if($file!="."&&$file!=".."&&is_dir("$dir/$file"))
    {
    add_dir("$dir/$file",$newzip);
    }
   }
 closedir($dh);
  }
} 

Quindi, in questo modo, posso creare un archivio ZIP "al volo", inserendovi una cartella "mydir":

include_once("zip.lib.php");

$myroot='/myroot/';
$mydir='mydir';

$newzip = new zipfile();
chdir($myroot);

add_dir($mydir,$newzip);

header("Content-Disposition: attachment; filename=".$mydir.".zip");
header("Content-Type: file/x-msdownload");
$data=$newzip->file();
header("Content-Length: ".strlen($data));
echo $data; 

Il problema è che, creando un archivio "grande", si incappa nel solito errore "MEMORY LIMIT EXCEED" ....

• Come potrei aggirare il problema??
• Si potrebbe modificare il metodo "file()" della classe "zipfile", in modo da spezzare i dati in parti più piccole??
• Oppure fare un output "poco alla volta", quando faccio "echo $data", alla fine del mio codice??
• Altre soluzioni??

Grazie!!