获取明天PHP的日期编号

To get the numerical representation of the 7 day week you do this :

echo date('N'); // 2 (Tuesday)

Is there a built in function to get tomorrow's numerical day?

I know how I could do it programatically, but I was wondering if there was a function to do this?

You could use date with strtotime, which can take a string expressing a relative date e.g.

echo date('N', strtotime('tomorrow'));

You can use DateTime() and modify() to +1 day:

$datetime = new DateTime();
$datetime->modify('+1 day');
echo $datetime->format('N');

Or alternatively just set the modification in DateTime() directly:

$datetime = new DateTime('+1 day');
echo $datetime->format('N');

Other relative date statements are available as well, such as tomorrow. These are detailed on the Supported Date and Time Formats: Relative Formats manual page.