Php programmer Interview Questions

It is easiest to explain that abstract classes can be used to define some basic skeleton for certain type, and interfaces are used to provide contract for additional functionality. So let's say you have abstract class User, and there some basic functions like getAge(), getEmail()... and that is OK, but if you want for your user be able to superhero, then you would implement martial arts interface, weapon manage interface. :) I am not talking about tech differences between abstract class and interfaces but the implementation, that is what would you should say on interview.

An interface merely defines a list of methods which must be provided along with the parameters those methods must accept. PHP Classes can implement multiple interfaces - declaring that it can be used as a parameter for other classes which require classes to implement either of the two interfaces. Every method defined in the interface must be implemented the class. An abstract class is much more complicated. It can, and frequently is, used like an interface. In addition to defining the method signatures, it can also define properties and constants that all subclasses will have available. However, PHP classes that choose to inherit from an Abstract class can only choose one such class. In addition, abstract classes can provide implementations for those methods. A common example is with methods used as true/false flags - an abstract class will implement all of them to return false. That way child classes only have to extend the method if they actually want to indicate true under some condition. Other methods may be fully implemented in an abstract class when there is a default way to perform them - allowing later coders to customize only when needed. But wait, there is more! Abstract classes are also frequently utilized as libraries of functions. Using static methods, it is possible to invoke those methods directly without needing to create a child class. This can be used to provide a simplified "namespace" - especially for versions of PHP which do not support namespaces. By collecting all the functions into an abstract class ThirdPartyName_Functions, then intuitive function names such as "printName" can be used without the fear of some other third party using the same function name. They can also be used as a registry/configuration object using static properties. For most cases, there is no need to have multiple connections to the primary database for every single class. Storing the connection in an abstract class allows only one connection to be used: MyRegistry::getDB() . Modern practice frowns on this in favor of Dependency Injection, where every class expects to be given a configuration object when created in order to retrieve this information.