PHP查询今日、昨日，本月、上月信息数量函数

function get_zhuti($cid,$day_num='',$addtime='')
{
/*
0 当天
-1 昨天
30 本月
-30 上月
*/
if ($addtime == ''){
$addtime = time();
}
if ($cid != ''){
$where="where cid=$cid";
}else{
$where="where 1=1";
}


if ($day_num == ''){
$sql1 = "select count(tid) AS num from tay_thread $where";
}
if ($day_num == "0"){
    $sql1 = "select count(tid) AS num  from tay_thread where to_days(date_format(from_UNIXTIME(`addtime`),'%Y-%m-%d')) = to_days(now())";
}
if ($day_num == "-1"){
    $beginYesterday = mktime(0, 0, 0, date("m"), date("d") -1, date("Y")); 
    $endYesterday = mktime(0,0,0,date("m") ,date("d"),date("Y"));//
    $sql1 = "SELECT count(tid) AS num FROM tay_thread WHERE  addtime BETWEEN '$beginYesterday' AND '$endYesterday'";
//echo $beginYesterday;
//echo "<br/>";
//$lll = date('Y-m-d H:i:s', $beginYesterday);
//echo $lll;
//echo "<br/>";
//$sss = date('Y-m-d H:i:s', $endYesterday);
//echo $sss;
//exit;
}
if ($day_num == "30"){
$beginThismonth = mktime(0, 0, 0, date("m"), 1, date("Y"));
$endThismonth = mktime(23, 59, 59, date("m"), date("d"), date("Y"));
    $sql1 = "SELECT count(tid) AS num FROM tay_thread WHERE addtime BETWEEN '$beginThismonth' AND '$endThismonth' ";


}
if ($day_num == "-30"){
$beginThismonth = mktime(0, 0, 0, date("m")-1, 1, date("Y"));
$endThismonth = mktime(23, 59, 59, date("m"), date("d")-date("d"), date("Y"));
    $sql1 = "SELECT count(tid) AS num FROM tay_thread WHERE addtime BETWEEN '$beginThismonth' AND '$endThismonth' ";
}


$result1=mysql_query($sql1);
$zhuti=mysql_fetch_array($result1);
    $page = array();
$page['num']      = $zhuti[0];
    return $page;
}