Variable variables on PHP

Sometimes it is convenient to be able to have variable variable names. That is, a variable name which can be set and used dynamically. A normal variable is set with a statement such as:


<?php
$a = 'hello';
?>


A variable variable takes the value of a variable and treats that as the name of a variable. In the above example, hello, can be used as the name of a variable by using two dollar signs. i.e.


<?php
$$a = 'world';
?>


At this point two variables have been defined and stored in the PHP symbol tree: $a with contents "hello" and $hello with contents…