php 格式化日期

function ShowDate($flag=0, $timestr=NULL)  
{  
    // 获取周几  
    $warr = array(  
    "0" => 星期日,  
    "1" => 星期一,  
    "2" => 星期二,  
    "3" => 星期三,  
    "4" => 星期四,  
    "5" => 星期五,  
    "6" => 星期六  
    );  
    $i = date("w", $timeStamp);  

    // 设置北京时间并获取时间戳  
    date_default_timezone_set('PRC');  
    $timeStamp = NULL;  
    if ($timestr)  
        $timeStamp = strtotime($timestr);  
    else 
        $timeStamp = time();  

    // 设置时间显示格式  
    $ret1 = date("Y年m月d日 H:m:s", $timeStamp) . " " . $warr[$i];  
    $ret2 = date("Y-m-d H:m:s", $timeStamp) . " " . $warr[$i];  
    $ret3 = date("y/m/d", $timeStamp);  
    $ret = $ret1; // 默认返回第一种  

    if ($flag == 2)  
        $ret = $ret2;  
    else if ($flag == 3)  
        $ret = $ret3;  

    return $ret;  
}
//该片段来自于http://outofmemory.cn