使用PHP中的SimpleImage调整图像大小

Question

I'm using SimpleImage to resize images in PHP. I need to resize the images uploaded via a form using the file browse. I use the following approach to resize the image uploaded via a file browse.

$image=new SimpleImage();
$image->load($_FILES['txt_brand_img']['tmp_name']); //It isn't working.

if($image->getWidth()>500)
{
$image->resizeToWidth(500);
$image->save("images_db/".$filename);
}

It isn't working. I could see somewhat resemble approach here but it didn't work for me. When I upload and save the image in a directory and give the saved file path to the load() function as follows it is working.

$filename=rand(1000,1000000).$_FILES["txt_brand_img"]["name"];
move_uploaded_file($_FILES["txt_brand_img"]["tmp_name"],"images_db/".$filename);

    $image=new SimpleImage();                       
    $image->load("images_db/".$filename);   //It is working.
    if($image->getHeight()>100 || $image->getWidth()>100)
    {                               
            $image->resize(100, 100);
        $image->save("images_db/thumb/".$filename);
    }
    else
    {
        $image->save("images_db/thumb/".$filename); 
    }

May I be using a wrong approach in the previous code snippet? How could the uploaded images be directly resized without saving them using SimpleImage?