PHP: check if class implements static method

Question

I need to check if a class implements specific method and then call it. If a method exists and is static it should be called static, otherwise it should be invoked on a class instance (object). The problem occurs when determining if a method is defined within a class as a static method.

Here is an example code that tests specific instance or class for method existence.

class A {
    public function b() {}

    public static function c() {}
}

$instance = new A();

var_dump(method_exists('A', 'b'));
var_dump(method_exists($instance, 'b'));

var_dump(method_exists('A', 'c'));
var_dump(method_exists($instance, 'c'));

var_dump(is_callable(['A', 'b']));
var_dump(is_callable([$instance, 'b']));

var_dump(is_callable(['A', 'c']));
var_dump(is_callable([$instance, 'c']));

When executed the output is as following:

bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)

The question is why the result is always true even if the callable argument is passed for static or non static call?

How to test if a method is defined as static without using Reflection?

I could use Reflection, but I'm trying to figure out why is_callable and method_exists are not working as stated in PHP documentation. Also, using Reflection could provoke performance issues. — Tez
– Tez, Commented Nov 11, 2014 at 10:57
@Tez PHP didn't have static methods from the first day. You can even call non-static methods from a static context (and vice versa), so of course these methods return true, because technically it is possible — kero
– kero, Commented Nov 11, 2014 at 11:01
@kingkero Yes, but it's not compliant to PHP strict standards, so I guess that approach won't work in this case. — Tez
– Tez, Commented Nov 11, 2014 at 11:09

Tofandel · Accepted Answer · 2020-02-05 10:27:09Z

10

A static function of a class is by definition a method of that class and it's also callable, hence calling method_exists or is_callable on a static method will always return true

For your use case you do not need to actually know if the method is static or not, calling

call_user_func([$instance, 'c']);

Will do what you want, if 'c' is a static method and $instance either an object or a class name, it will be called 'statically'

Similarly, if you're calling

call_user_func([$instance, 'b']);

If 'b' is a non static method and $instance an object, the method will be called on the object 'non statically'

If you really need to know if the method is static or not, then you should use Reflection which is doing excellent in term of performances, against your beliefs

$rm = new \ReflectionMethod($instance_or_class, 'b');
$rm->isStatic();

edited Feb 5, 2020 at 10:27

answered Mar 2, 2019 at 14:42

Tofandel

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1 Comment

dave Over a year ago

thanks! used ReflectionMethod to check isStatic() for runkit_method_add() to stub methods in an old/poorly designed code base in desperate need of coverage; runs great and helped keep things simple (don't have to specify whether the method is static or not for every test).

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