PHP - Hashable Functions

Hashable is an interface that can allow objects to be used as keys. It is an alternative to the spl_object_hash() function that determines an object’s hash based on its handle: this means that two objects that are considered equal by an implicit definition can't be treated as equal because they are not the same instance.

The hash() function can be used to return a scalar value to be used as an object's hash value that determines where it goes in the hash table. While this value doesn't have to be unique, objects that are equal must have the same hash value.

The equals() function can be used to determine if two objects are equal. It is guaranteed that the comparing object can be an instance of the same class as the subject.

Interface synopsis

Ds\Hashable {
   /* Methods */
   abstract public bool equals( object $obj )
   abstract public mixed hash( void )
}