my script is
<?
$sorgente="./Immagine1.jpg";
$destinazione="./immago.jpg";
$size = getimagesize("./Immagine1.jpg");
if($size[0] > $size[1]){
$newWidth=718;
$newHeight=538;
}
else{
$newWidth=538;
$newHeight=718;
}
$imS=imagecreatefromjpeg($sorgente);
$sX=imagesx($imS);
$sY=imagesy($imS);
$imD=imagecreatetruecolor($newWidth,$newHeight);
imagecopyresampled($imD,$imS,0,0,0,0,$newWidth,$newHeight,$sX,$sY);
imageJPEG($imD,$destinazione);
imagedestroy($imS);
imagedestroy($imD);
unlink($sorgente);
?>