Variable Variable

Question

Hi all, I don't understand this especial in this example
<?php
$a = 'hello';
$hello = "Hi!";
echo $a;

// Outputs 'Hi!'
?>

Answer 1

Since $a is "hello", then $a can be thought of as:

$($a) - - > $(hello) - - > $hello

Since $hello is "Hi!", then so is $a.