When do you add an entry to the CHANGELOG.php file, and what do you put into it? 

When you fix an artefacts, solve a problem or add new logic you need to enter a short description in the CHANGELOG.php file. When you for instance fix several artefacts after each other in one day, please make one entry using your name, and collect all changes to the entry.

We have a legend in the file to roughly describe what the commit was:

* -> Security Fix
# -> Bug Fix
+ -> Addition
^ -> Change
- -> Removed
! -> Note

If you are fixing a tracker bug, then you'd put the hash (#) followed by the title of the tracker item.

You just need enough to give an overview of what was changed.  If you did a commit to fix or add language strings in 20 or 30 files, that could easily be covered by:

 # Fixed missing language strings

However, if you change something like rename a function/method/class, then you should really list each instance and not just put a general "renamed lots of classes".  Just go over the messages that are there and you should get the hang of it. If in doubt just describe what you did in a little more detail - better to have too many words than not enough.  The changelog will be cleaned when we go stable anyway. 

A typical entry looks like:

DD-MM-YY Name of developer

 # Bug fix descriptio

 ^ Change

 ! Note, most of the times a remark that you need to re-install or something familiair.

p.s. this info will be included in the development strategy document later on