Question

We can restrict type of method parameters; for example, we should say that function parameter should be an instance of object described in class with name “Some Class”.

function some_function(Some_Class $object) {
}

Is there any php native posibilities to restrict method parameter with two or more classes? For examle, “Some Class” or “Some Class2” or “Some Class3”.

Or maybe there is any way to restrict method parameter with classes which implements interface with name “Some_Interface”?

Thank you.

Answer 1

You can do it with an interface, e.g.

interface LoggableInterface
{
    public function log($message);
}

Some classes implementing the interface

class FileLog implements LoggableInterface { 
    public function log() { /* code to log to File ... */ }
}

class DbLog implements LoggableInterface { 
    public function log() { /* code to log to Db ... */ }
}

class SysLog implements LoggableInterface { 
    public function log() { /* code to log to SysLog ... */ }
}

Then you can use it as a TypeHint like this:

function some_function(LoggableInterface $anyLogger);

This way you make sure the param passed to some_function() has a method log(). It doesn’t matter which concrete you pass to it (FileLog, DbLog or SysLog), but just that these classes implement the interface.