There are already some comments on using sprintf to force leading leading zeros but the examples only include integers. I needed leading zeros on floating point numbers and was surprised that it didn't work as expected.
Example:
<?php
sprintf('%02d', 1);
?>
This will result in 01. However, trying the same for a float with precision doesn't work:
<?php
sprintf('%02.2f', 1);
?>
Yields 1.00.
This threw me a little off. To get the desired result, one needs to add the precision (2) and the length of the decimal seperator "." (1). So the correct pattern would be
<?php
sprintf('%05.2f', 1);
?>
Output: 01.00
Please see http://stackoverflow.com/a/28739819/413531 for a more detailed explanation.

$formatted = sprintf("%01.2f", $money);