PHP uploads images and sets transparent image watermark effects

$im = imagecreatefromjpeg($_file["upload"]["tmp_name"]); //Picture
$watermark = imagecreatefrompng("Smiley.png"); //Watermark image Path
$im_x = imagesx($im);
$im_y = imagesy($im);
$w_x = imagesx($watermark);
$w_y = imagesy($watermark);
imagecopy($im,$watermark, $im_x-$w_x,$im_y-$w_y,0,0,$w_x,$w_y);
imagejpeg($im); //You can add a path to save the watermarked image
< p>//Use type to determine the image type
//switch($_file["upload"]["type"])
//case:1
//Other gd library functions
//imagejpeg() corresponds to jpeg
 //imagegif() corresponds to gif
//imagepng() corresponds to png
imagedestroy($im);