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Date: Sat, 19 Dec 2009 11:20:29 +0100
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Subject: Re: [PHP-DEV] is_a() versus instanceof
From: johannes_m@gmx.net ("Johannes Mueller")

Johannes "Schlüter" wrote:
> On Sat, 2009-12-19 at 01:42 +0100, Johannes Mueller wrote:
>> if($foo instanceof bar){
>> ..
>> }
>> // runs without any notification
>
> instanceof is a language construct expecting a class identifier.
> It doesn't complain about on-existing classes as it would need to
> trigger the __autoloader which might be way too much.
>
>> and
>>
>> if(is_a($foo, bar)){
>> ..
>> }
>> // runs with an undefined constant bar notification
>
> is_a() is a function expecting a string. And this warning is unrelated
> to the fact that the class "bar" doesn't exist, but due to the way PHP
> treats undefined constants.

Thank you for your answers, that is what I've expected. Unfortunately this 
is sometimes annoying when using namespaces, where you have to take care of 
the namespaces too.

I do understand the performance impact of a more complex solution and my 
fault was to mix two different operations. I expected instanceof and is_a() 
to check if the class exists.

My personal problem was, that I didn't recognized instanceof to treat the 
requested class as a normal string, even it is not enclosed by quotation 
marks.

The only protective barrier in this case seems to be a skilled IDE, that 
helps you to avoid referencing non existant classes.

Cheers
Johannes