Compresser un dossier avec ces sous dossiers

Fatal error: Allowed memory size of 12582912 bytes exhausted (tried to allocate 4352052 bytes) in /web/htdocs/www.mm2x.com/home/mmfc/pclzip.lib.php on line 2427

et quand je rafraichi la page j'ai cette erreur:
Fatal error: Allowed memory size of 12582912 bytes exhausted (tried to allocate 23148438 bytes) in /web/htdocs/www.mm2x.com/home/mmfc/sauvegarde_fichiers.php on line 69

Je vous donne le code de la page sauvegarde.php car je l'ai modifié sachant que mes dossiers ne sont pas les mêmes:
<?

/*
This script is made to synchronise a test server with a production server.
It takes all the file newly uploaded on a server since last execution and servs them in a zip file.
The zip file contains the tree structure of the file. So you just need to unzip the file on your test server
Please think to correctly chmod your $archive_name path
*/
// Name of your archive file :
$archive_name=mktime().'.rar';

// path to archive : (relative path is better but absolute is also possible)
$tab_path_to_arch=array(
                        '../mmfc/');


// <Read the date of last archive session>
$saved_file = fopen('sauvegarde.cf','r');
$LIMIT_DATE=fread($saved_file,filesize ('sauvegarde.cf'));
fclose($saved_file);
// </Read the date of last archive session>

// Defines is better than global or parameter in function
define('_LIMIT_DATE',$LIMIT_DATE);

// Set the next save date until now.
// IMPORTANT TO DO THIS BEFORE STARTING SAVING
$LIMIT_DATE_FOR_NEXT_TIME=mktime()-3600; // security of one hour for the fun

// user information
echo 'Save new files since :'.date('d/m/y - h:i',$LIMIT_DATE).'<br />';
echo 'The archive file will be created as : '.$archive_name.'<br />';

// <Search the file to archive>
$tab_files_to_arch=array('');
foreach($tab_path_to_arch as $lcl_root){
    list_dir($lcl_root,$tab_files_to_arch);
    echo '<br />..........................<br />';
}
// </Search the file to archive>

// <make the archive file>
if (sizeof($tab_files_to_arch)==1) die ('Nothing new today. Exiting');
require('pclzip.lib.php');
$archive = new PclZip($archive_name) or die ("FAUTE initialisation de l'archive");
$archive -> create($tab_files_to_arch) or die ("FAUTE creation archive");
// </make the archive file>

// <save the date for next archive session>
$save_file = fopen('sauvegarde.cf','w');
fwrite($save_file,$LIMIT_DATE_FOR_NEXT_TIME);
fclose($save_file);
// </save the date for next archive session>

// <finishing the script>
$size=round(filesize($archive_name)/1024,2);
echo '
<br />
<a href="'.$archive_name.'">Download the archive file ('.$size.'Ko)</a>';
// </finishing the script>

// tests the date of a file and adds it to the table if needed
// path : path and name of the file
// file : file name (just for display)
// tableau : address param containing a list of files to compute
// returns none : the table will contain all infos
function test_date($path,$file,&$tableau){
//    echo 'file to test : '.$file;
    $theone=file($path);
    if (filemtime($path) > _LIMIT_DATE) {
        $tableau[]=$path;
        echo $file.' ';
    }
    return;
}

// Lists the file of a path (recursive method)
// path : path to scann
// tableau : address param containing a list of files to compute
// returns none : the table will contain all infos
function list_dir ($path,&$tableau){
    if ($dir = @opendir($path))    {
        echo '<b>'.$path.'</b><br />';
        while($file = readdir($dir)) {
            if ($file !="." && $file != "..") {
                $path_file=str_replace($_SERVER['DOCUMENT_ROOT'],"",$path);
                $path_file=str_replace("/","\\",$path_file);
                if (is_dir($path."/".$file)) { list_dir ($path.'/'.$file, $tableau);}
                else { test_date($path.'/'.$file,$file,$tableau); }
            }
        }
        closedir($dir);
    } else {
        echo $path.' isn\'t dir;';
    }
    return;
}
?>

J'ai regardé les différents façon de pouvoir corriger ce problème comme par exemple:
<?
//valeur initiale
echo "get_cfg_var(memory_limit) = ".@get_cfg_var('memory_limit')."<br />";
echo "ini_get(memory_limit) = ".@ini_get('memory_limit')."<br />";

//modification
@ini_set("memory_limit",'18M');
// on tente d'allouer 18 M

//modification prise en compte ?
echo "get_cfg_var(memory_limit) = ".@get_cfg_var('memory_limit')."<br />";
echo "ini_get(memory_limit) = ".@ini_get('memory_limit')."<br />";
// on verifie si l'allocation de 18 M a pu etre possible sur le serveur
?>

Mais la fonction ini_set() semble être désactivé.

Donc si le zip me prend trop de ressource, je me suis dis qu'il valait mieux y mettre en gz grâce à la ZLIB mais je ne sais pas du tout comment ça fonctionne. Merci de m'aider