Best program of life

ab.php

<?php

  $Bar = "a";
  $Foo = "Bar";
  $World = "Foo";
  $Hello = "World";
  $a = "Hello";

  echo $a; //Returns Hello
  echo $$a; //Returns World
  echo $$$a; //Returns Foo
  echo $$$$a; //Returns Bar
  echo $$$$$a; //Returns a
  echo $$$$a; //Returns Bar
  echo $$$a; //Returns Foo
  echo $$a; //Returns World
  echo $a; //Returns Hello

  $b = 'Hello';
  $$b = 'World';
  $$$b = 'My';
  $$$$b = 'Friend';

  echo "${b} ${$b} ${${$b}} ${${${$b}}}"; //Returns Hello World My Friend