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Date: Wed, 11 Aug 2004 23:52:16 -0400
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CC: Dan Ostrowski <dan@ostrowski.cc>,  internals@lists.php.net
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Subject: Re: [PHP-DEV] is_a() vs. instanceof
From: hans@velum.net (Hans Lellelid)

Alan Knowles wrote:

> I think he's referening to something like this (which is common in pear):
> 
> $x = $someobj->somemethod();
> if ($x instanceOf PEAR_Error) {
>   .......
> }
> 
> while that code is redundant in the case of exceptions, it is still a 
> valid situation.. that $x may be a valid return, and PEAR_Error was 
> never loaded..


Yup, that's exactly what I'm talking about.

I want to be able to do this:

if ($db instanceof DBPostgres) {
   /// do something funky specific to Postgres
}

If My DB adapter is DBMySQL, I don't want to load the DBPostgres adapter 
just so I can test whether my object is of that type ...

and checking first whether class_exists('DBPostgres') just seems kinda 
kludgy & straying from the "problem domain" ... especially since $db 
instanceof DBPostgres would *always* be false if DBPostgres isn't loaded.

Hans