PHP get minDateTime from array

Question

I've written a function to get the smallest date from an date[ ] and check for null. If null == infinity

    /**
     * @param DateTimeInterface|null ...$dates
     * @return DateTime|null
     */
    public static function minDateTime(?DateTimeInterface ...$dates)
    {
        $dateList = [];
        $dates = array_filter($dates);
        if (empty($dates)) {
            // all values where null
            return null;
        }

        foreach ($dates as $date) {
            $dateList[] = $date->getTimestamp();
        }

        return (new DateTime())->setTimeStamp(min($dateList));
    }

Its working but could this be written smaller or with more comments, so that external coworkers can read this?

The $dateList = []; at the start of the function isn't needed. — Dave
– Dave, Commented May 14, 2020 at 17:01

mickmackusa · Accepted Answer · 2020-05-14 23:26:26Z

Things to be aware of:

array_filter() does a full loop of the array.
foreach(), of course, does a full loop of the array.
min() does a full loop of the array.
empty() does a couple of things: it checks if a variable is not set AND if it is "falsey". Because the $dates variable will be unconditionally set, there is no need to check this -- just use !$dates if you want to check if the array is empty.
array_filter(), like empty() is a "greedy" seeker of "falsey" values. I assume that this is a non-issue for your task because there should be no 0 or false (etc.) values -- only datetime values or nulls.
datetime objects can be compared.
you don't need to make iterated calls to getTimestamp(), nor do you need to declare a new datetime object and set its time manually -- just use the one you found.

I suppose I'll recommend that you loop the data just one time. No array generation, no function calls, very direct and concise. Your custom method name is descriptive. Go with this:

Code: (Demo)

public static function minDateTime(?DateTimeInterface ...$dates)
{
    $minDate = null;
    foreach ($dates as $date) {
        if ($date && (!$minDate || $date < $minDate)) {
            $minDate = $date;
        }
    }
    return $minDate;
}

This was really helpfull. Didn't know until now that null == false. That did not cross my mind for years. Thanks for additional information on the different loops, too! — CasualBen
– CasualBen, Commented May 15, 2020 at 6:45

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