Jason Barnett wrote:
Think of declaration of properties and methods as a "contract". When something is public it is available to all of PHP. When it is private it is only usable by the class that you define it in. When it is protected it is a hybrid; it is usable to the class that defined it and it can be "inherited" by classes that extend that class.
So, decide what level of access you really *need* for that property / method. If a property is only supposed to be modified by class methods (for example, a password string) then make it private or possibly protected. If everything is public access then there is temptation to do something like:
Back in the day, I used to code in C++
Nothing irked me more than some so-called programmer who would over-zealously make every damned thing private.
I'd go and sub-class it, and want to make my extended class actually USEFUL and be ham-strung by his short-sightedness.
Punk. ;)
You know as well as I do that is the reason why we have protected members. And it is also why we use PHP: because we can quickly change the source to fit whatever are our new requirements. Actually I find myself using public / protected members about 90% of the time... reserving private members only for things that just don't make sense in a subclass. Or, things that *should* be different in a subclass (for example, DSN information on a database class).
So when you ask yourself "Self, should this be public, protected, or private?" make sure you phrase it as:
"Can I think of ANY way in the future that some other cool programmer would want to do fun and interesting and useful things with this?"
Let the flames begin :-)
The roof. The roof. The roof is on fire. ;)
Isn't everything in life a trade off? As I see it using private vs. protected vs. public is a tradeoff between flexibility and maintainability. If a member is private and its value is somehow messed up, well I know that it had to have been messed up somewhere in *that* class. If it's protected then the possible error points include the subclasses. If it's public, well then I could have goofed up anywhere (and believe me I DO!)
Call me crazy, but didn't someone just a few weeks ago suggest you try to LIMIT the number of places where a bug can be found? ;)
But I digress. I said it before and I'll say it again: it's a trade off.
-- Teach a man to fish...
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