PHP datetime add 6 months and 1 year - php

Question

I have a date set using PHP datetime like this..
$originaldate = 2019-01-10 17:52:17
$converted = DateTime::createFromFormat("Y-m-d H:i:s", $originaldate);
The date is successfuly converted into a PHP DateTime object, now I am trying to add create 2 new dates that are 6 months and 1 year ahead of this date.
Whats the best way to achieve this?

Answer 1

You should look into php class DateInterval http://php.net/manual/en/class.dateinterval.php
Here's an example:
$converted = DateTime::createFromFormat("Y-m-d H:i:s", $originaldate);
$converted1Year = $converted->add(new DateInterval("P1Y"));//add one year //object reference is the same so adding a year altered original object and a reference to it is passed back, not copied
$converted2 = DateTime::createFromFormat("Y-m-d H:i:s", $originaldate);
$converted6months = $converted2->add(new DateInterval("P6M")); // add 6 months
And as suggested in the comments here's the DateTimeImmutable equivalent:
$converted = DateTimeImmutable::createFromFormat("Y-m-d H:i:s", $originaldate);
$converted1Year = $converted->add(new DateInterval("P1Y"));
$converted6Months = $converted->add(new DateInterval("P6M"));

Answer 2

Check out DateTime::add
$converted->add(new DateInterval("P18M")); // add 18 months
P18M means 18 month interval

Answer 3

You can clone the time to create a duplicate and use DateTime::modify to change the new date.
Try this;
$sixMonths = clone $converted;
$sixMonths->modify('+6 months');
$oneYear = clone $converted;
$oneYear->modify('+1 year');

Answer 4

$converted = $converted->modify('+6 months');
$converted = $converted->modify('+1 year');

Answer 5

Like so:
$sixMonths = date('Y-m-d', strtotime($converted. ' + 6 months'));
$oneYear = date('Y-m-d', strtotime($converted. ' + 1 year'));

Answer 6

The format already default ("Y-m-d H:i:s"). You don't need to use CreateFromFormat, unless you are handle data from 3rd party. My suggestion for the code would be like this
$originaldate = '2019-01-10 17:52:17';
$converted = new DateTime( $originaldate ); //prefer like this
//DateTime::createFromFormat("Y-m-d H:i:s", $originaldate); //after browsing this is recomended
$date6Month = new DateTime( $originaldate );
$date1Year = new DateTime( $originaldate );
$dateBack = new DateTime( $originaldate );
//$date6Month = $date1Year = $dateBack= $converted;
//prefer to use different variable for every date. Not copy
echo "ori:".$converted ->format('Y-m-d H:i:s') . "\n";
//ori:2019-01-10 17:52:17
##6 month later
$date6Month ->add(new DateInterval('P6M'));
echo "6 month:".$date6Month ->format('Y-m-d H:i:s') . "\n";
//6 month:2019-07-10 17:52:17
##1 year later
$date1Year ->add(new DateInterval('P1Y'));
echo "1 year:".$date1Year ->format('Y-m-d H:i:s') . "\n";
//1 year:2020-01-10 17:52:17
//1 year:2020-07-10 17:52:17 (wrong if using copy main parameter)
$date1Year ->add( DateInterval::createFromDateString('1 Years') );
echo "1 year (later):".$date1Year ->format('Y-m-d H:i:s') . "\n";
//1 year (later):2021-01-10 17:52:17
//1 year (later):2021-07-10 17:52:17 (wrong if using copy main parameter)
you can use DateInterval::createFromDateString for readable code than using format. My suggestion is to separated the variable not copy from the origin.
The format you can use on DateInterval
Start "P" when contain Day, Month and Year
Format
Info
Example
Y
Year
1Y
M
Month
3M
D
Day
5D
example: P1Y3M5D
Always Start "P" before "T" if not contain Day, Month and Year (PT1H). If not start it with "T"
Format
Info
Example
H
HOUR
1H
M
MINUTES
3M
S
SECONDS
5S
F
MICROSECOND (php7+)
5F
example: PT1H3M5S
wrong: T1H3M5S
other example (from link below)
date_default_timezone_set('America/Phoenix');
//is important to add when your time are detail
$date = new DateTime('2000-01-01');
$date->add(new DateInterval('P7Y5M4DT4H3M2S'));
echo $date->format('Y-m-d H:i:s') . "\n";
//2007-06-05 04:03:02
$originaldate = 2019-01-10 17:52:17
$dateBack = $dateBack2 = new DateTime( $originaldate );
//if you want to substract the value you can use this
$dateBack ->sub(new DateInterval('P1Y2M3DT1H4M1S'));
echo $dateBack ->format('Y-m-d H:i:s') . "\n";
//output: 2019-05-07 16:48:16
$dateBack2=$converted;
$formatDay='P1Y3M6D'; //only year, month and day
$formatTime='T1H3M6S'; //only hour, minutes and seconds
$dateBack2 ->sub(new DateInterval( $formatDay.$formatTime ));
echo $dateBack ->format('Y-m-d H:i:s') . "\n";
//2018-02-01 15:45:10
as mention on the phpmanual, there is other format (microtime) that's not include on this example.
related link
Date Time PHP
Date Interval
Format on Interval
Date Interval create using String