Eat my monkeydust

The yaml file parser will attempt to parse all the values, rather than taking them as they are - which in most cases is a good thing, however you must remember to use quotes when the intended output is a string, and the parser may interpret the value otherwise:

default_culture:   en
// No problem, en is treated as a string 
// and /en/ is automatically added to links
 
default_culture: no
// Oops, no is translated by Symfony 
// the same way as false, 0 or off, giving it a boolean value!
 
default_culture: 'no'
// That's better, now you will have the intended results.

The same applies to any yml files that you may have “keywords” in, so try to always use quotes round everything that is not boolean, integer, etc.

Something that just cropped up today…

As your site grows, and you add more and more config to the app.yml file, be very careful not to re-declare the same named element. Symfony will not warn you, and there will be no errors - but the second (lower) instance will simple overwrite the first!

For example, if you have forgotten that you already have an element called profile hiding near the top of the file, and you add another one called profile at the bottom, with all your profile page settings - the lower one will destroy the one higher in the file.

This can be hard to spot if you have been meticulously coding and added a default value to all your sfConfig::get() calls because chances are when you are developing the site, all your defaults will be the same as the ones you have specified in app.yml.

The problem will become apparent when an end user tries to change the configuration and the change is ignored, because Symfony is simply using the default value rather than the one the user thinks they are setting.

Careful out there kids!