php关于正则表达式的事

<?php
date_default_timezone_set("Asia/Shanghai");
$string = 'kemo|addidas|就是这样的|haha|2013-12-13 09:00:09|weobo|lail';
$patterns = array();
$patterns[0] = '/2013-12-13 09:00:09/';
$patterns[1] = '/weobo/';
$patterns[2] = '/lail/';
$replacements = array();
$replacements[2] = date('Y-m-d H:i:s',time());
$replacements[1] = 'tengx';
$replacements[0] = 'buyao';
echo preg_replace($patterns, $replacements, $string);
?>

kemo|addidas|就是这样的|haha|2013-12-14 11:40:43|tengx|buyao 

<?php
date_default_timezone_set("Asia/Shanghai");
$string = 'kemo|addidas|就是这样的|haha|2013-12-13 09:00:09|weobo|lail'; 
$pattern = '/\d{4}-\d{2}-\d{2}\s+\d{2}:\d{2}:\d{2}/';
$replacement = date('Y-m-d H:i:s',time());
echo preg_replace($pattern, $replacement, $string);
?>

kemo|addidas|就是这样的|haha|2013-12-14 12:07:55|weobo|lail