Variable Variables

During a recent project I discovered a totally new concept in programming for myself,
variable variables. I needed to update multiple records from one page. After banging
my head on the wall for quite some time, I stumbled across the variable variable and
all my troubles went away!

Introduction

So, just what the heck is a variable variable anyway? According to the PHP manual,
a variable variable takes the value of a variable and treats that as the name of a
variable. While this may seem pretty straightforward, it can be a little confusing
with so many uses of the word “variable” in one sentence. What the definition simply
states is that you can set a variable — x equals this — and then set the variable
variable, meaning you set the value of x as a new variable of x. In this example,
the variable this would equal is cake. In PHP, this would be denoted as follows:

<?php
$x = "this";
$$x = "is cake";
?>

The $$ is the syntax used in PHP for a variable variable. I can now call the two variables $x and $$x two ways.

<?php
echo "$x ${$x}";
?>

 

<?php
echo "$x $this";
?>

Both of these will return the string “this is cake”. Notice that $$x is written as ${$x}
in echo. This lets PHP know that you are using the variable $$x and not $ and $x.

Still scratching your head? Or maybe you get it, but want a more in depth and actually
useful example? In the next section I will show you how variable variables may be used
to edit multiple records on one page.