php picture zoom implementation method

php Basic Exercise - Image Zoom:

<?php
    /**
    * image zoom.
    */
    function imageZoom($filename, $w, $h) {
        /* Arguments meaning */
        /* $filename: the source of the name */
        /* $w: you want get the image's width */
        /* $h: you want get the imgage's height */
        $arr = getimagesize($filename);
        $src_w = $arr[0];
        $src_h = $arr[1];
        $src_t = $arr[2];
        /*1 = GIF . 2 = JPG . 3 = PNG . 4 = SWF . 5 = PSD . 6 = BMP . 7 = TIFF(intel byte order) . 
= TIFF(motorola byte order) . 9 = JPC . 10 = JP2 . 11 = JPX . 12 = JB2 . 13 = SWC . 
= IFF . 15 = WBMP . 16 = XBM*/
        $src_m = $arr['mime'];
        $src_img = imagecreatefromjpeg($filename);
        if (($w / $src_w) >($h / $src_h)) {
            $bili = $h / $src_h;
        } else {
            $bili = $w / $src_h;
        }
        $dst_w = $src_w * $bili;
        $dst_h = $src_h * $bili;
        $dst_img = imagecreatetruecolor($dst_w, $dst_h);
        imagecopyresampled($dst_img, $src_img, 0, 0, 0, 0, $dst_w, $dst_h, $src_w, $src_h);
        header("content-type:{$src_m}");
        switch ($src_t) {
            case 1:
                $imgout = "imagegif";
                break;
            case 2:
                $imgout = "imagejpeg";
                break;
            case 3:
                $imgout = "imagepng";
                break;
            default:
                echo "The type was wrong!";
                break;
        }
        $dst_filename = "s_".$filename;
        $imgout($dst_img, $dst_filename);
        imagedestroy($dst_img);
    }
    $filename = 'gg.jpg';
    imageZoom($filename, 100, 200);

Core: < 1 > Pay attention to how the scaling is achieved, although the resulting image may be a little different than expected, but at least the scaling is guaranteed.

< 2 > Type of control.