Ragazzi ecco la soluzione per coloro che in futuro avranno questo problema futuro

Codice PHP:
case 3:
//PNG
$immagine = date("dmyHis").".png";
$image_p = imagecreatetruecolor($finalsizew, $finalsizeh);  
$image   = imagecreatefrompng($file['tmp_name']);
imagealphablending($image_p, false);
imagesavealpha($image_p,true);
$transparent = imagecolorallocatealpha($image_p, 255, 255, 255, 127);
imagefilledrectangle($image_p, 0, 0, $finalsizew, $finalsizeh, $transparent); 
imagecopyresampled($image_p, $image, 0, 0, 0, 0, $finalsizew, $finalsizeh, $width, $height);
imagepng($image_p, $file['tmp_name']);  
imagedestroy($image);
imageDestroy($image_p);
break;