PHP合并两张图片（水印）

$dst_im = "http://img6.cache.netease.com/photo/0001/2016-04-15/BKMTUO8900AP0001.jpg";
        $src_im = "https://ss0.bdstatic.com/5aV1bjqh_Q23odCf/static/superman/img/logo/logo_white.png";
 
        $dst = imagecreatefromstring(file_get_contents($dst_im));
        $src = imagecreatefromstring(file_get_contents($src_im));
        list($src_w, $src_h) = getimagesize($src_im);
        //imagecopymerge($dst, $src, 10, 10, 0, 0, $src_w, $src_h, 50);
        imagecopy($dst, $src, 150, 630, 0, 0, $src_w, $src_h);
        
        
        list($dst_w, $dst_h, $dst_type) = getimagesize($dst_im);
        switch ($dst_type) {
            case 1://GIF
                header('Content-Type: image/gif');
                header('Content-Disposition: inline; filename="barcode.gif"');
                imagegif($dst);
                break;
            case 2://JPG
                header('Content-Type: image/jpeg');
                header('Content-Disposition: inline; filename="barcode.jpg"');
                imagejpeg($dst);
                break;
            case 3://PNG
                header('Content-Type: image/png');
                header('Content-Disposition: inline; filename="barcode.png"');
                imagepng($dst);
                break;
            default:
                break;
        }
        imagedestroy($dst);
        imagedestroy($src);
        exit;