September 3rd, 2010
(written by lawrence krubner, however indented passages are often quotes). You can contact lawrence at: email@example.com
99% of the work I do involves PHP, yet I still find some of its behavior odd. I am sympathetic to this Faggruppe post:
I suspect the current isset() behaviour was implemented by someone that thought it was a great idea to implement the same logic in the isset() function. However – there are several situations where a variable would be assigned a null value, and calling isset() on that variable would then return false. In my opinion, a variable is only not isset() if unset() has been called on it. In all other cases, it is set, even if it is set to a null value.
There is of course no fix for this intended behaviour – as changing this isset() behaviour would cause a complete backwards compatibility break – so watch out for those isset() statements.
PS: This flawed logic is not applied to property_exists(). AFAIK, there is no “variable_exists” – this is what isset() is for, and the documentation for property_exists() actually mentions this. Fail x 2, but props for pointing it out in the manual.