PHP マニュアル: Determines whether an object is equal to the current instance

abstract public bool Ds\Hashable::equals(object $obj)

Determines whether another object is equal to the current instance.

This method allows objects to be used as keys in structures such as Ds\Map and Ds\Set, or any other lookup structure that honors this interface.

注意:
It's guaranteed that obj is an instance of the same class.

警告

It's important that objects which are equal also have the same hash value. See Ds\Hashable::hash.

obj: The object to compare the current instance to, which is always an instance of the same class.

true if equal, false otherwise.