I have image upload site
But the problem is that I have thumb image after uploading from the function
imagecreatefromgif/png/jpeg()
But the problem how can i do a thumb image from bmp format too because the function imagecreatefrombmp() does not existing

Do not use GD functions to resize images. Use imagemagick's convert utility.

why not

You gave at least one reason in your original post. Another reason is that convert is fool-proof: if some dumb user uploads 10Mpx photo and some dumb webmaster does not check image filesize the convert utility will resize it as if nothing happened while the GD will definitely crash with "out of memory".

Not even mentioning that compiled command-line utility is several times faster than a php script and offers more flexibility if you will need not to simply resize images one day.