Image upload and resize problems

Came across a problem in an application where 6 large photos were being uploaded and resized simultaneously. I suspected it was a memory problem, as it’s been working fine for a long time. I increased  upload_max_filesize in php.ini, which half-worked – I could now upload 2 large images, but not 6 like I needed to. Turned out I needed to increased post_max_size too (again in php.ini).

Note that if upload_max_filesize is exceeded then ['tmp_name'] fields in $_FILES will be blank.

One other thing worth mentioning that I came across when working on the same application a while ago is I found I also had to increase memory_limit (in php.ini) way beyond its default to allow php enough memory to resize big image files.