Signature Compatibility Exception

All methods must be compatible with their parent’s signature: the types, reference options, variadic and number must be compatible (although, not equal).

The exception are constructors, which may be completely different from their parent’s. This is for backward compatibility.

And this rule also has the exception that abstract constructor, in interfaces and abstract parent classes, must be compatible, and their signature are enforced. Normal constructor are free.

See Also

• constructors

• compatible or not? [Try me]

PHP Features

• constructor

• abstract

• interface

• inheritance