part 13 / 13 : And a bit more but really useful

0) install easy xdebug:
https://addons.mozilla.org/en-US/firefox/addon/easy-xdebug/
which permit you to command the connection between xdebug and PDT from an icon in the browser, really useful! You can have a debugging session of aptana running and launch the PHP debugger at the same time.

1) setup firefox to disable the cache:
in firefox, in tools->options

in the tab "advanced"
in the tab "Network"
set to 0  the space for the cache.

In my case, it was not enought to avoid firefox to cache my page. I had to open the config:
In firefox, write about:config as an adress,
in the filter write: 'cache', and look for network.http.use-cache, and double click it to set it to false. Double clicking it again will set it to true and re-enable the cache.
Here the page where I found the explanations:
http://benlancaster.wordpress.com/2009/02/10/how-to-completely-disable-firefox-cache/

2) about PDT and Xdebug:
To get the values of the variables when you are debugging inside a function:
In the variables view, you can see all the variables you have inside the function but not the values of them. To get the ones you want, open the "Expressions" view and add the variables you need. BUT it becomes very unstable if you have lines with expressions or variables that are not in the function. For example, if you have a javascript variable as an expression, the debugger scratch.