upload "facoltativo"

[Stepunk]

Come posso fare in modo che in un form l'upload sia facoltativo?


Io ho un form i cui c'è un campo "immagine" nel quale si seleziona un'immagine jpg dal proprio harddisk, però non deve essere obbligatorio!

Ho usato queste due classi:

class Image{
    var $src_filename;
    var $src_witdh;
    var $src_height;
    var $src_type;
    var $src_attr;
    var $src_image;  

    function Image($filename){
        $this->src_filename = $filename;
        $this->GetImageInfo();
    }

    function GetImageInfo(){
        list($this->src_width,$this->src_height, $this->src_type, $this->src_attr) = getimagesize($this->src_filename);
    }

    function CreateSourceImage(){
        switch($this->src_type){
            case 1:
                $this->src_image =imagecreatefromgif($this->src_filename);
                   break;
            case 2:
                $this->src_image =imagecreatefromjpeg($this->src_filename);
            break;
            case 3:
                $this->src_image =imagecreatefrompng($this->src_filename);
            break;
            default:    return false;
        }
        return true;
    }

    function SaveProportionateImage($filename, $quality, $width){
        if ($width < $this->src_width){
            $dest_width = $width;
            $ratio = $this->src_width / $dest_width;
            }
        else {
            $ratio=1;
            $dest_width = $this->src_width;
            }
        $dest_image = imagecreatetruecolor($dest_width, $this->src_height / $ratio);
        imagecopyresampled($dest_image, $this->src_image, 0, 0, 0, 0,
            $this->src_width / $ratio,
            $this->src_height / $ratio,
            $this->src_width,
            $this->src_height);
        imagejpeg($dest_image, $filename.'.jpg', $quality);
        imagedestroy($dest_image);
    }
    
    function SaveProportionateImageAll($filename, $quality, $width){
        if ($this->src_width > $this->src_height && $width < $this->src_width){
            $dest_width = $width;
            $ratio = $this->src_width / $dest_width;
            }
        else if($width < $this->src_height){
            $dest_width = $width;
            $ratio = $this->src_height / $dest_width;
            }
        else{
            $ratio=1;
            $dest_width = $this->src_width;
            }
        $dest_image = imagecreatetruecolor($this->src_width / $ratio, $this->src_height / $ratio);
        imagecopyresampled($dest_image, $this->src_image, 0, 0, 0, 0,
            $this->src_width / $ratio,
            $this->src_height / $ratio,
            $this->src_width,
            $this->src_height);
        imagejpeg($dest_image, $filename.'.jpg', $quality);
        imagedestroy($dest_image);
    }
    function SaveProportionateImageAllConcerti($filename, $quality, $width){
        if ($this->src_width > $this->src_height && $width < $this->src_width){
            $dest_width = $width;
            $ratio = $this->src_width / $dest_width;
            }
        else if($width < $this->src_height){
            $dest_width = $width;
            $ratio = $this->src_height / $dest_width;
            }
        else{
            $ratio=1;
            $dest_width = $this->src_width;
            }
        $dest_image = imagecreatetruecolor($this->src_width / $ratio, $this->src_height / $ratio);
        imagecopyresampled($dest_image, $this->src_image, 0, 0, 0, 0,
            $this->src_width / $ratio,
            $this->src_height / $ratio,
            $this->src_width,
            $this->src_height);
        imagejpeg($dest_image, $filename, $quality);
        imagedestroy($dest_image);
    }

    function Free(){
        imagedestroy($this->src_image);
    }
} 

class FileUpload{
    var $up_dir;        //la directory temporanea in cui verrà uploadata l'img
    var $filename;    //il nome del file
    var $new_filename;    //il nuovo nome del file se vogliamo rinominarlo
    
    function FileUpload($up_dir){
        $this->up_dir = $up_dir;
    }

    function RenameFile($new_filename){
        $this->new_filename = $new_filename;
    }

    function Upload($files){
        if(!file_exists($this->up_dir))
            die('
ERRORE: La directory non esiste! Contatta il [email="webmaster@novarawakeup.it"]webmaster[/email] e digli cosa ti è successo!
 [url="javascript:history.go(-1)"]<-Torna indietro[/url]');
        $this->filename = ($this->new_filename) ? $this->new_filename :$files['name'];
        if(trim($files["name"]) == "")
            die("
ERRORE: Non hai indicato il file da uploadare!
 <a href=\"javascript:history.go(-1)\"><-Torna indietro</a>");
        if(is_uploaded_file($files["tmp_name"])){
            move_uploaded_file($files["tmp_name"],$this->up_dir."/".$this->filename)
            or die("
ERRORE: Impossibile spostare il file; controlla l'esistenza o i permessi della directory! Contatta il <a href=\"mailto:webmaster@novarawakeup.it\">webmaster</a> e digli cosa ti è successo!
 <a href=\"javascript:history.go(-1)\"><-Torna indietro</a>");
        }else
            die ("
ATTENZIONE: Problemi nell'upload del file ".$files["name"].". Contatta il <a href=\"mailto:webmaster@novarawakeup.it\">webmaster</a> e digli cosa ti è successo!
 <a href=\"javascript:history.go(-1)\"><-Torna indietro</a>");
    }
    
    function DeleteFile(){
        unlink($this->up_dir . '/' . $this->filename);
    }
} 

Nela classe file upload c'è questo controllo sul fatto di aver selezionato un file:
if(trim($files["name"]) == "")
die("
ERRORE: Non hai indicato il file da uploadare!
<a href=\"javascript:history.go(-1)\"><-Torna indietro</a>");

se lo tolgo mi da comunque un errore nell'upload!



Come modifico i controlli in modo da rendere l'upload facoltativo?
Grazie
Ste