PHP Design Patterns PHP OO This and Parent Basics

PHP This and Parent Basics

Here are examples of using this and parent to call functions in a class. Using $this-> a class calls functions in itself, using parent:: a class calls functions in it's parent class.

If you are used to Java or other OO languages you might expect parent:: to be $super->, but with PHP it is not. Maybe super wasn't used to avoid confusion with superglobals. I don't know why :: is used instead of -> for non static calls.

OOPHPParentClass.php

//copyright Lawrence Truett and FluffyCat.com 2007, all rights reserved


  //OOPHPParentClass - a simple OO PHP Class which is extended by OOPHPChildClass
  
  class OOPHPParentClass {  
    
    public function getColor() {
      return 'RED';
    }


  }

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OOPHPChildClass.php

//copyright Lawrence Truett and FluffyCat.com 2007, all rights reserved


  //OOPHPClass - a simple OO PHP Class which extends OOPHPParentClass


  include_once('OOPHPParentClass.php');


  class OOPHPChildClass extends OOPHPParentClass {      


    public function getColor() {
      return 'BLUE';
    }  
    
    public function getParentColor() {
      return parent::getColor();
    }


  }

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testOOPHPThisParent.php

//copyright Lawrence Truett and FluffyCat.com 2007, all rights reserved


  include_once('OOPHPChildClass.php');


  define('BR', '<'.'BR'.'>');


  echo 'TESTING OOPHPThisParent'.BR;
  echo BR;
  
  $childClass = new OOPHPChildClass();
  
  echo 'test 1 - show the child color'.BR;
  echo $childClass->getColor();
  echo BR.BR;


  echo 'test 1 - show the parent color'.BR;
  echo $childClass->getParentColor();
  echo BR.BR;


  echo 'END TESTING OOPHPThisParent'.BR;

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output of testOOPHPThisParent.php

TESTING OOPHPThisParent


test 1 - show the child color
BLUE


test 2 - show the parent color
RED


END TESTING OOPHPThisParent

References

Design Patterns
Design Patterns by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides

PHP 5
The Official PHP web site
Core PHP Programming, 3rd Edition by Leon Atkinson and Zeev Suraski

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