DateTime: add, how do you cause a failure to return FALSE

[sgsmallman]

Title is pretty self explanatory, i know that DateTime: add returns a DateTime object in your preferred format.

But I want to return false. Dose anyone know how to do so

[jstern]

Maybe its not as self explanatory as it sounds.. from php.net

 

"Return Values

 

Returns the DateTime object for method chaining or FALSE on failure."

 

It returns false on failure by default.