php

Access Identifiers
 public : This is the default and undeclared value  
private: Can be accessed in the class itself. 
protected : can be accessed in the child class  

static : variable can be used using :: operator , no class instantiation is required for functions., eg  User: : $name; 
abstract: These classes can not be used as such but need to be extened.
final : stops further modification. 
iterateObject : This method let iterate instances of all objects.

Online Playgrounds for php

  1. http://sandbox.onlinephpfunctions.com/
  2. http://phpfiddle.org/
  3. https://www.tehplayground.com