how to add 0's to a number

I want to add 0s to a number.

Let's say I have 5, I have to add 4 digits like this:
00005

If I have 17 I have to add 3 digits like this:
00017

str_pad :)

PHP Code:

---

<?php
$num = 9;
echo str_pad($num, 5, "0", STR_PAD_LEFT);

$num = 17;
echo str_pad($num, 5, "0", STR_PAD_LEFT);
?>

---

PHP Code:

---

$num = 5;
$zeros = "0000";

echo $zeros.$num;

$num = 17;
$zeros = "000";

echo $zeros.$num; 


---

$r = sprintf('%05d', $number);