It should be something like this:
<?
if( !$outFile=fopen("C:/Apache/htdocs/wiro/calendar.html','a'))
{
echo "Could not open file!";
exit;
}
echo "Open file Successfully!";
?>
Or if you want to include calendar.html into the php script this will do:
<?php
require("C:/Apache/htdocs/wiro/calendar.html");
?>