[php] PHP prepend leading zero before single digit number, on-the-fly

PHP - Is there a quick, on-the-fly method to test for a single character string, then prepend a leading zero?

Example:

$year = 11;
$month = 4;

$stamp = $year.add_single_zero_if_needed($month);  // Imaginary function

echo $stamp; // 1104

You can use str_pad for adding 0's

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

string str_pad ( string $input , int $pad_length [, string $pad_string = " " [, int $pad_type = STR_PAD_RIGHT ]] )

The universal tool for string formatting, sprintf:

$stamp = sprintf('%s%02s', $year, $month);

http://php.net/manual/en/function.sprintf.php