PHP 在单个数字前添加前导零，即时

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

例子:

$year = 11;
$month = 4;

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

echo $stamp; // 1104

推荐答案

你可以使用 sprintf: http://php.net/manual/en/function.sprintf.php

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