pad number out with 0s

[echousername]

how do i take a number in php and pad it out with 0s? like, 1 becomes 0001,

thanks

[Loafin]

function leading_zero($length,$number){
  $length=$length-strlen($number);
for ($i = 0; $i < $length; $i++){
     $number = "0" . $number;
     }
  return($number);
  }

"leading_zero(3,15)" returns "015"

This answer is courtesy of the manual

[echousername]

very nice, thanks

[dopey]

or use str_pad(): http://www.php.net/manual/en/function.str-pad.php