Visibility

What is Visibility? Visibility within a class is basically an option that allows you to give different user permission levels to functions and variables. There are 3 different options for visibility: Private - can only be accessed within that class Protected - can only be accessed within that class and child classes Public - can be accessed by all code

By default, PHP uses Public in class programming, but it is always a good idea to declare visibility to give your coding easier viewing to others.

The visibility option goes before the variable name of before the function definition, as shown below:

<?php Class someClass  {     

   public $var1 = "Hi, I'm public"; 
   protected $var2 = "Hi, I'm protected"; 
   private $var3 = "Hi, I'm private >:D"; 

   public function sayPublic() { 

      echo("I'm public!");   

      }   

   protected function sayProtected() { 
      echo("I'm protected!"); 

      }  

  private function sayPrivate() { 
      echo("I'm private >:D !");    

      } 

} ?>

So, we can call anything that is public without problem, being able to call sayPublic() and $var1 and output them outside of the class.

Now, if we call the private variable, we will get this error in PHP:

Fatal error: Cannot access private property someClass::$var in C:\Server\www\Visibility\PrivateExample.php on line 17

and a private function called will result in:

Fatal error: Call to private method someClass::sayPrivate() from context '' in C:\Server\www\Visibility\PrivateExample.php on line 17

now the same kind of error will occur with a protected variable and function as well, just saying "Call to protected method" or "Cannot access protected property".

Now, what we can do though is echo out and return private and protected variables in public functions:

<?php Class someClass  {   

    

   public $var1 = "Hi, I'm public";    protected $var2 = "Hi, I'm protected";    private $var3 = "Hi, I'm private >:D"; 

   public function sayPrivateVar() {  

       echo $var3;  

        }         

   

      public function sayProtectedVar() {    

         echo $var2;   

        } 

} ?>

We can, as I said before, call child classes to use the functions as well:

<?php Class someClass  {   

  

       protected function sayHi() {   

        $this->var = "Hello";      

        retun $this->var;    

        } 

} 

Class someExtendedClass extends someClass {

    

    public function sayHi($someName) { 

       echo(parent::sayHi()); 

       echo(" $someName");    

     } 

}       
 ?>

  Conclusion:

  Private members can only be accessed from inside the   
  class itself.

  Protected members can only be accessed from inside the   class it self and its child classes.

  Public members can be accessed from anywhere - outside   the class, inside the class it self and from child classes.

on Wednesday, May 14, 2014