codice:
$imgname="test.jpg";
$dim=getimagesize($imgname);
$x=400;
$y=300;
// SPESSORE BORDO
$bordo=10;
$src_img=imagecreatefromjpeg($imgname);
$im=Imagecreatetruecolor($x,$y);
// COLORE BORDO
$black = imagecolorallocate($im, 0, 0, 0);
imagefilledrectangle($im, 0, 0, $x, $y, $black); 
imagecopyresampled($im, $src_img, $bordo, $bordo, 0, 0, $x-(2*$bordo), $y-(2*$bordo), $dim[0], $dim[1]);
header("content-type: image/jpeg");
imagejpeg($im,"",50);
imagedestroy($im);