可以透出php的info資訊

程式碼開頭原本是<?改成<?php網頁會變空白

程式碼內容如下
"<?
include("calendar.php");

class MyCalendar extends Calendar
{
function getCalendarLink($month, $year)
{
$s = getenv('SCRIPT_NAME');
// Redisplay the current page, but with some parameters
// to set the new month and year
return "$s?month=$month&year=$year";

}
function getDateLink($day, $month, $year)
{ 	
	$link = "";
    // Only link the first day of every month 
	include("setup.php");
	$conn=mysql_connect( $mysql_server_name, $mysql_username, $mysql_password);
	$sql="SELECT * FROM `semester`";
	$db=mysql_select_db($mysql_database,$conn);
	mysql_query('SET NAMES utf8');
	$result=mysql_query($sql,$conn);
	while($row=mysql_fetch_row($result))
	{
	$temp1[0]=substr($row[1],0,4);
	$temp2[0]=substr($row[2],0,4);
	if($temp1[0]==$year || $temp2[0]==$year)
	{
	$temp1[1]=substr($row[1],5,2);
	$temp1[2]=substr($row[1],8,2);
	$temp2[1]=substr($row[2],5,2);
	$temp2[2]=substr($row[2],8,2);

	if(mktime(0,0,0,$month,$day,$year)>=mktime(0,0,0,$temp1[1],$temp1[2],$temp1[0]) && mktime(0,0,0,$month,$day,$year)<=mktime(0,0,0,$temp2[1],$temp2[2],$temp2[0]))
	{
		if($month<10)$month="0".$month;
		if($day<10)$day="0".$day;
        $date=$year."-".$month."-".$day;
        $link = "classinfo.php?date=$date";
    }
	}
	
	}
   
        
    return $link;
}

}

$d = getdate(time());

//add by alvin 20110105 for correct date select.
$year = $_GET['year'];
$month = $_GET['month'];
//add by alvin 20110105 for correct date select.

if ($month == "")
{
$month = $d["mon"];
}

if ($year == "")
{
$year = $d["year"];
}

$cal = new MyCalendar;
echo $cal->getYearView($year);

?>

跑出PHPINFO的資訊。代表PHP可以正常運行。
但你將其改成<?PHP就會報錯。(其實空白頁因該就是有錯誤了)
可能是有些函數沒載入或是不支援。
看到你還有用 mysql_connect 系列的函式。
推測你的PHP版本是7版，不支援MYSQL相關函數而造成問題。

可試著降版到5.6試試，並查看你的PHPINFO是否有對應的MYSQL庫的載入。5版的正常會預先載入。
7板的已經不會自動載入了。但會有PDO的應用。