I have a wordpress like php script, that is installed just like wordpress - from the browser.
This script mkdir's folder and in this folder needs write permissions on certain files.

But 50% of the time (on different servers) , the script fails to install because it doesn't have the write permission on those files.

Q1. Why doesn't it have the required permissions? it successfully created a folder , so shouldn't it have write permissions on every file in the folder ?

Q2. Who is the owner of such a folder/files ? www-data ?
Q3. What is the ideal way to install these wordpress like scripts, as far as permissions are concerned ?

I have half a day to fix this issue. Please Help!

Edit:I asked my 'boss' and he revealed the script isn't installed via a script on my most occasions, but simply copied to the server via ftp. i.e unzip on local -> then transfer the unzipped files to server via ftp.

Cant say anyone can understand your question ? you yourself looks confused..
so with the data provided i can say:
As long as you are running the scripts as auser that has permissions to write to the directory, the script will run good.

you better know that, do a ls -l on that directory to find out.

Run as a usre that has required set of permissions or run as root.

well full day passed now