PHP: How to split a number to multiple strings

I want to split a long number which i got into multiple strings in PHP. I got this:

<?php
$this = 020420151230;
?>

I want to get this result:

//output:
    $this['day'] = 02;
    $this['month'] = 04;
    $this['year'] = 2015;
    $this['hour'] = 12;
    $this['minute'] = 30;

Can you please help and advice which function should i use for this?