i need some practical examples of cases when i could use the observer pattern when developing a website.. (using php) I have one "when a user publishes an Article (subject), the class RSS and the class EMAIL (the observers) will modify the rss and send an email to the admin", but i'm not even sure if this is a good example..where are you using the observer pattern?BTW: this is not a homework, i was just lying here thinking about this pattern 
EDITEDI'm more curious about the "WHEN to do it" and not the "HOW to do it"
EDITEDI'm more curious about the "WHEN to do it" and not the "HOW to do it"