add leading zeros in php

$number = 4;
str_pad($number, 2, '0', STR_PAD_LEFT); // returns 04

$number = 14;
str_pad($number, 2, '0', STR_PAD_LEFT); // returns 14

str_pad($month, 2, '0', STR_PAD_LEFT); 

<?php
$num = 4;
$num_padded = sprintf("%02d", $num);
echo $num_padded; // returns 04
?>

sprintf('%06d', '12')