Why does Apache + PHP require execution permissions to write to a file?

Question

It has always baffled me that if a folder has read and write permissions, Apache + PHP can't write to it. You have to end giving apache execution permissions to be able to write a file in that folder. Why?

For example with chmod 664 (where the build group includes the apache user) apache won't be able to write a temporary cache file in this folder:

drw-rw-r--  5 jenkins build 4096 Jun 15 13:05 cache

while with chmod 774 apache will be able to write a new file to the folder:

drwxrwxr--  5 jenkins build 4096 Jun 29 11:44 cache

Answer 1

You need execute permission to conceptually enter a directory (cd into it, list files within, etc.). It would have been clearer if they called this bit something else for directories. This article recommends thinking of it as the "search" permission on directories.

Answer 2

When these permission are set for a directory it gives ability to access metainfo and accessing to contents I think this is why you need execute.