PHP - type hinting for object, not the same as stdClass

Question

Is it just me or is this behavior weird in PHP. Lets say for instance that we have a function like this:

function test(object $arg)
{}

If I were to call this function:

test((object)'string');

object (the type hinting) would not refer to a stdClass and would result in an error even though object seems to be a reference to stdClass when looking at the built in settype() function in PHP. Even casting to an object would result in a stdClass but for some reason I can't use settype($foo, 'stdClass')...

Is there a reason behind this?

and type object is not a string, (string)'bla', (object){any:1} — Álvaro Touzón
– Álvaro Touzón, Commented Feb 14, 2017 at 10:26

miken32 · Accepted Answer · 2017-02-15 00:50:38Z

1

There is no overall object class definition in PHP. Even if you were to create a class called myClass and give an instance to the test function the code would not work. The typecast to object creates an instance of type stdClass.

You have to use function test(stdClass $arg) as the function definition.

edited Feb 15, 2017 at 0:50

miken32

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answered Feb 15, 2017 at 0:28

mcq8

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3 Comments

Saruman Over a year ago

I know how it works, I'm wondering why the keyword object even exists... When using it as a type hinting it doesn't refer to stdClass but when casting to a object it results in a stdClass... Why not just remove the keyword and cast to stdClass, and if they want to keep it, why allow it to be used as a type hinting when nothing will actually match?

mcq8 Over a year ago

Because you are allowed to make a class called object if you want. PHP does not know in advance what classes will be defined. The object becoming an stdClass is just how it works, you cast to an "object" and not a string for example.

Saruman Over a year ago

That is even worse, that would mean that "object" means different things depending on if there is already a class named object or not. But thanks for the answer

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