is_object + instanceof

I’ve been trying hard, but I can’t see why this common code in MODx uses both tests:



It would seem that an instance of an object class would have to be an object so the is_object() test seems unnecessary.

Does this code work in PHP4?

Is it a speed thing? I imagine that most of the time the object passes the test so you’d have a net loss in speed by using both tests.

Quote from: BobRay at Mar 31, 2010, 05:46 AM

I’ve been trying hard, but I can’t see why this common code in MODx uses both tests:

if (is_object($object) && $object instanceof xPDOObject) {

It would seem that an instance of an object class would have to be an object so the is_object() test seems unnecessary.

Does this code work in PHP4?

Is it a speed thing? I imagine that most of the time the object passes the test so you’d have a net loss in speed by using both tests.

No, it’s an error thing, you can’t check a non-object with instanceof or it throws a PHP error; both checks are necessary. The first says, is this in object, the next says is it an instance of the class I want.

Thanks. I knew I was missing something.

I didn’t know that the short-circuiting was guaranteed in PHP and was confused by all the examples like this that came up:



On closer inspection, I see that they’re all preceded by an is_object() test.

What if you know the object does exist or the function would never be called? For example, in a plugin using OnLoadWebDocument? You know that $modx->resource will necessarily exist. All you want to do is check if it's a modStaticResource, for example.

Sanity tests are always at the discretion of the coder.

The is_object() test only takes a few milliseconds (possibly microseconds), though. Your case seems safe enough, but I've been bitten when somebody else (e.g., Setup) invoked an event I had a plugin tied to and the standard objects ($modx->user or $modx->resource) didn't exist.

That can happen pretty easily with scripts that run outside of MODX, instantiate it, then call MODX processors.