From your experience
what has been hardest thing to do as a php programmer?
(generating ideas for.....may be Social network like "whats new" section.......or may be "handling replicated servers operation" ....or providing very generic customization features to users...


what do you think is the hardest..?
and
what has been hardest in your experience..?

(ok,i agree in depends on many things...so hardest may be ..with took lots of time...needed lots of brain stroming...)