Facade

Intent

provide a simple interface to a subsystem.

Motivation

a complex system can have many parts that need to be exposed, but it could be confusing ergo - provide a simple interface to the system. For example a read-evaluate-print process of an interpreter

Implementation

Hide the construction of the required objects inside the facade

Example

class rep_facade {
   function __construct() {
     $this->firewall = new firewall();
     $this->reader = new reader();
     $this->evaluator = new evaluator();
     $this->printer = new printer();
   }

   function rep($text) {
     $text = $this->firewall($text);
     $ts   = $this->reader($text);
     $result = $this->evaluator($ts);
     return $this->printer($result);
   }
 }

Complications

The lack of modules and/or nested classes in php means that this is a comfort interface, not an enforcing interface