DateTime PHP

When I search and read code about time and date problems developers have, I noticed that a lot of people still use the old PHP functions like date(), time() or strtotime().

What about using DateTime instead?

It’s time to introduce this powerful PHP object.

DateTime can do all the usual date and time operations you could ask for and even more. Using DateTime can save a lot of time when you have to do more complex operations on dates.

Now I see you asking: why using DateTime instead of a bunch of PHP date functions?

Here’s why:

• The object DateTime is definitely more robust to use. Less bug is always better.
• DateTime is an object. You can use composition or inheritance to modify his behavior easily. You need always the same date as input for your unit tests? Use your own dummy datetime object which always return the birthday of your dog!
• Using one object is more clear for your fellow developer colleagues. Even if they don’t know DateTime, they just have to look to the documentation for one single object. It is definitely better than looking for the documentations of three different functions!

DateTime instantiation and formatting

The instantiation is easy: you can pass to the constructor a date correctly formatted, or nothing if you want to use the actual date and time.

Here the list of supported date and time formats you can inject in the constructor.

You can then format the date in order to display it, in two lines of code:

$dateTime = new DateTime('2016-01-01');
echo $dateTime->format('Y-m-d H:i:s');`

Output: 2016-01-01 00:00:00

$dateTime = new DateTime();
echo $dateTime->format('Y-m-d H:i:s');`

Output: whatever the current date is, correctly formatted.

Easy, isn’t it? You can as well precise the timezone you want as a second argument:

$date = new DateTime('2016-05-20', new DateTimeZone('Europe/Berlin'));

DateTime and timestamps

You want to format an unreadable timestamp into a nice and shiny easy-to-read date?

$dateTime = new DateTime();
$dateTime->setTimestamp(1271802325);
echo $dateTime->format('Y-m-d H:i:s');

Output: 2010-04-20 22:25:25

Obviously you can as well output a timestamp if you need to:

$dateTime = new DateTime('2016-05-20');
echo $dateTime->getTimestamp();

Output: 1271802325

Adding or subtracting a chunk of time

What about adding or retrieving a day, a minute, an hour of a date? You only need to use the proper formatting:

$dateTime = new DateTime('2016-01-01');
$dateTime->modify('+1 day');
echo $dateTime->format('Y-m-d H:i:s');`

Output: 2016-01-02 00:00:00

You can as well use the constructor if you work on the current date:

$dateTime = new DateTime('+1d');
echo $dateTime->format('Y-m-d H:i:s');`

Output the current date plus one day.

For the same result you could as well instantiate a DateInterval object but you would have to use an interval specification which is way harder to read.

I never use this last solution personally, simply because I never need to.

Difference between two dates

DateTime objects can as well be used to compare dates. It’s where DateTime can be really, really handy.

$datetime1 = new DateTime('2009-10-11 12:12:00');
$datetime2 = new DateTime('2009-10-13 10:12:00');
$interval = $datetime1->diff($datetime2);
echo $interval->format('%Y-%m-%d %H:%i:%s');

Output: 00-0-1 22:0:0

In this example we created two DateTime objects. They will receive two different dates in their constructors.

In order to compare those two dates we use the method diff() of the first DateTimeobject with the second DateTime object as argument.

The diff() method will return a new object of type DateInterval. If you want to format the difference between the two dates, you can use as well the format() method of the DateInterval object but be careful: it won’t accept the same formatting as the DateTime::format() method.

The output indicate that there is 1 day and 22 hours difference between the two dates.

If you only want the seconds, hours or day of interval you can write:

$datetime1 = new DateTime('2009-10-11 12:12:00');
$datetime2 = new DateTime('2009-10-13 10:12:00');
$interval = $datetime1->diff($datetime2);
echo $interval->s;
echo $interval->h;
echo $interval->d;

Output:

0
22
1

Compare DateTime objects

If you need to compare two DateTimes, it’s as simple as that:

<?php

$datetime1 = new DateTime('2009-10-11 12:12:00');
$datetime2 = new DateTime('2009-10-13 10:12:00');

if ($datetime1 > $datetime2) {
    echo 'datetime1 greater than datetime2';
}

if ($datetime1 < $datetime2) {
    echo 'datetime1 lesser than datetime2';
}

if ($datetime1 == $datetime2) {
    echo 'datetime2 is equal than datetime1';
}

Output: datetime1 lesser than datetime2

Original font: https://thevaluable.dev/php-datetime-create-compare-format/