I came across this answer for how to use interfaces and traits in unison: http://stackoverflow.com/a/9205347

Could someone explain to me or suggest some reading material as to how abstract classes fit into that answer? Do interfaces and traits used together remove the need for abstract classes?

When is it best to use abstract classes over interfaces and traits? When is it best to use interfaces and traits over abstract classes?

Edit: Thanks to everyone who responded. You have been very welcoming to a new redditor.

I understand a base class provides common methods to other classes that extend it.

And from what I've read, Interfaces provide a way to make sure that a method exists in your class.

It seems that Abstract class combines the two into a single file, so I'm a bit confused on when to use what.

Let's say I have a method called get_device() that is shared amount LaptopDevice, DesktopDevice, and MobileDevice classes.

Each device class gets a list of devices from its device type.

Would I do something like:

abstract class AbstractDevice {
   public function get_device() {
       return $this->device;
   }
}

class MobileDevice extends AbstractDevice {
}

or this

class Device implements DeviceInterface {
    public function get_device() {
       return $this->device;
    }
}

class MobileDevice extends Device implements DeviceInterface {
}