Thursday, January 24, 2013

PHP: Public, Protected and Private

These three keywords define the visibility of variables.

  • public: visible for both inside and outside
  • protected: visible only to its own methods
  • private: similar to protected, intended to be accessed only by the class who defines it

An Instance

class foo{
   public    $a=1;
   protected $b=2;
   private   $c=3;

   function stampa()
      echo $this->b;
      echo $this->c;
class bar extends foo{
   function __construct(){
      $this->b = 4;
      $this->c = 5;
$A = new foo;
echo $A->a;
$B = new bar;

Here is the output,



  • The version of tested php: 5.3.6-13
  • The instance shows the re-assigning of the private member doesn't make any difference. The inheriting class can not modify private members.
  • The private member is still visible (printed) to the inheriting class.

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