<?php
$string = 'April 15, 2003';
$pattern = '/(\w+) (\d+), (\d+)/i';
$replacement = '${1}1,$3';
echo preg_replace($pattern, $replacement, $string);
?>
这里$replacement 里$replacement = '${1}1,$3'; 代表什么意思?! 还有$pattern = '/(\w+) (\d+), (\d+)/i';最后那个/i又是什么意思?!