doesn't work sprintf

[eluser]WanWizard[/eluser]
I can't explain. You say that your $dates array contains

Array
( [2010-04-01] => 2
[2010-04-09] => 7
[2010-04-11] => 5
[2010-04-25] => 0
)

So all I can say is that PHP is right: the requested index does not exist. So either your code to fill $dates is wrong, or you need to check if the index exists before referencing it.