PHP multiple classes implementing same interface

Question

If I have an interface in PHP, say

interface AuthenticationInterface {
}

and two classes which implement the interface, for example

class ApiKey implements AuthenticationInterface {
}

class AuthToken implements AuthenticationInterface {
}

How is it determined which of these classes is used when a new AuthenticationInterface in instantiated?

You can't instantiate interfaces directly; you have to explicitly pick an implementing class to instantiate. — Austin
– Austin, Commented Oct 15, 2014 at 6:03
I don't get why you received a negative vote for the question. You are clearly new to programming and instead of receiving guidance, you get a negative mark. WTF Stackoverflow? — Dan
– Dan, Commented Oct 15, 2014 at 6:13

Dan · Accepted Answer · 2014-10-15 06:14:54Z

6

Interfaces are used to define a structure(architecture) for classes that inherit it.

An interface is a contract specifying a set of methods, fields and properties which will be available on any implementing object

I think you were interested in the class factory design pattern. Read more about it here: php design patterns

edited Oct 15, 2014 at 6:14

answered Oct 15, 2014 at 6:09

Dan

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Comments

user4094161 · Accepted Answer · 2014-10-15 06:04:24Z

0

Interface can't be instantiated. You can create object of class.

answered Oct 15, 2014 at 6:04

user4094161

Comments

user1269942 · Accepted Answer · 2014-10-15 06:27:06Z

0

If your object was instantiated for you somewhere upstream and all you know is that it implements your AuthenticationInterface interface(so you know it can be one of a small number of classes...2 in your case), you can tell which class your object is by using "instanceof"

if ($your_object instanceof ApiKey)
{
    echo 'object class is ApiKey';
}

answered Oct 15, 2014 at 6:27

user1269942

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