Php Image Resize

function my_image_resize($src_file, $dst_file, $dst_width=32, $dst_height=32) { 
    if($dst_width <1 || $dst_height <1) { 
        echo "params width or height error !"; 
        exit(); 
    } 
    if(!file_exists($src_file)) { 
        echo $src_file . " is not exists !"; 
        exit(); 
    } 

    $type=exif_imagetype($src_file); 
    $support_type=array(IMAGETYPE_JPEG , IMAGETYPE_PNG , IMAGETYPE_GIF); 

    if(!in_array($type, $support_type,true)) { 
        echo "this type of image does not support! only support jpg , gif or png"; 
        exit(); 
    } 

    switch($type) { 
        case IMAGETYPE_JPEG : 
            $src_img=imagecreatefromjpeg($src_file); 
            break; 
        case IMAGETYPE_PNG : 
            $src_img=imagecreatefrompng($src_file);         
            break; 
        case IMAGETYPE_GIF : 
            $src_img=imagecreatefromgif($src_file); 
            break; 
        default: 
            echo "Load image error!"; 
            exit(); 
    } 
    $src_w=imagesx($src_img); 
    $src_h=imagesy($src_img); 
    $ratio_w=1.0 * $dst_width/$src_w; 
    $ratio_h=1.0 * $dst_height/$src_h; 
    if ($src_w<=$dst_width && $src_h<=$dst_height) {
        $x = ($dst_width-$src_w)/2;
        $y = ($dst_height-$src_h)/2;
        $new_img=imagecreatetruecolor($dst_width,$dst_height); 
        imagecopy($new_img,$src_img,$x,$y,0,0,$dst_width,$dst_height); 
        switch($type) { 
            case IMAGETYPE_JPEG : 
                imagejpeg($new_img,$dst_file,100);
                break; 
            case IMAGETYPE_PNG : 
                imagepng($new_img,$dst_file); 
                break; 
            case IMAGETYPE_GIF : 
                imagegif($new_img,$dst_file); 
                break; 
            default: 
                break; 
        } 
    } else { 
        $dstwh = $dst_width/$dst_height; 
        $srcwh = $src_w/$src_h;
        if ($ratio_w <= $ratio_h) {
            $zoom_w = $dst_width; 
            $zoom_h = $zoom_w*($src_h/$src_w); 
        } else { 
            $zoom_h = $dst_height; 
            $zoom_w = $zoom_h*($src_w/$src_h); 
        } 

        $zoom_img=imagecreatetruecolor($zoom_w, $zoom_h); 
        imagecopyresampled($zoom_img,$src_img,0,0,0,0,$zoom_w,$zoom_h,$src_w,$src_h); 
        $new_img=imagecreatetruecolor($dst_width,$dst_height); 
        $x = ($dst_width-$zoom_w)/2;
        $y = ($dst_height-$zoom_h)/2+1;
        imagecopy($new_img,$zoom_img,$x,$y,0,0,$dst_width,$dst_height);
        switch($type) { 
            case IMAGETYPE_JPEG : 
                imagejpeg($new_img,$dst_file,100);
                break; 
            case IMAGETYPE_PNG : 
                imagepng($new_img,$dst_file); 
                break; 
            case IMAGETYPE_GIF : 
                imagegif($new_img,$dst_file); 
                break; 
            default: 
                break; 
        }
    }
}