I had been using the image resize class written by someone else to resize images or to create the thumbnails, here is the link to the class I had been using.
http://www.
The problem is that your memory is getting full if you try to resize a very large image with GD library.
You sould use ImageMagick. use the following code
exec("source -resize size destination");
So if you want to resize logo.gif with a maximum size of 64x64 and rename it to resize_logo.gif
exec("convert logo.gif -resize 64x64 resize_logo.gif");
For more information follow this link