A way to calculate DateTime intersection where NULL is possible

Question

Background

I'm integrating Limesurvey with an application, where new survey tokens are added directly to the Limesurvey database. Before insertion can be done, I need to check that a given set of tokens (with validfrom and validuntil attributes) in Limesurvey does not intersect with a given range of dates (DateTime).

The problem

Since Limesurveys token validfrom and validuntil attributes can be NULL, a simple comparison of DateTime can't be done, or can it?

(A Limesurvey validfrom/validuntil NULL value implies "always")

What I have

A php class that checks if the Limesurvey attributes are NULL (or not), and returning a calculation of the intersection as needed.

Code: http://phpfiddle.org/main/code/3vp-j3b

(It's what's inside the foreach loop, lines 34-70, that are interesting here)

What I ask

Is there a way to improve/optimise this method, given that the comparison values are special?

Answer 1

You could replace null with a possible first and last date to ease comparing:

if (is_null($token['validfrom']) {
    $token_validfrom = new DateTime('0000-01-01 00:00:00');
} else {
    $token_validfrom = new DateTime($token['validfrom']);
}
if (is_null($token['validuntil']) {
    $token_validuntil = new DateTime('9999-12-31 23:23:59');
} else {
    $token_validuntil = new DateTime($token['validuntil']);
}

This way only your last line of comparison should be necessary:

return ($validfrom == $token_validfrom) || ($validfrom > $token_validfrom ? $validfrom < $token_validuntil : $token_validfrom < $validuntil);