PHP Add 4 hours to date [duplicate] - php

Question

This question already has answers here:
Add hours to datetime in PHP
(1 answer)
How to add an hour onto the time of this datetime string?
(3 answers)
php string in a date format, add 12 hours
(4 answers)
Closed 1 year ago.
I'm trying to add four hours to a date but the resultant time is incorrect
$date = $dates[0] < $dates[1] ? $dates[1] : $dates[0];
$new_date = date("Y-m-d H:i:s", strtotime('+4 hours', $date));
echo $date;
echo "<br/>". $new_date;
The result i'm getting is
2015-09-17 09:36:18
1969-12-31 20:33:35
The first date is correct but the second isn't, it should be 4 hours ahead of the first

Answer 1

Does this work?
$date = $dates[0] < $dates[1] ? $dates[1] : $dates[0];
$new_date = date("Y-m-d H:i:s", strtotime('+4 hours', strtotime($date)));
echo $date;
echo "<br/>". $new_date;
You were passing $date AS the second argument of strtotime, and it's not a UNIX timestamp (as you said). So with strtotime again, you should convert it in a UNIX timestamp, and then pass it to strtotime.

Answer 2

Add timestamps to a timestamp, not to a date string.
echo date("Y-m-d H:i:s", strtotime('+4 hours', strtotime("2015-09-17 09:36:18")));
^
Fiddle
That is the right syntax. You can simplify it however with
echo date("Y-m-d H:i:s", strtotime('2015-09-17 09:36:18 +4 hours'));
Fiddle

Answer 3

You're using strtotime incorrectly. Its second argument MUSt be a unix timestamp:
php > var_dump(strtotime('+4 hours', 12345));
int(26745)
php > var_dump(strtotime('+4 hours', '2015-09-17 09:36:18'));
PHP Notice: A non well formed numeric value encountered in php shell code on line 1
int(16415)
Your call should be
php > var_dump(date('r', strtotime('2015-09-17 09:36:18 + 4 hours')));
^^^^^^^^^^^
string(31) "Thu, 17 Sep 2015 13:36:18 -0500"
php >

Answer 4

Both other answers are correct.
Not seeing what you have in your $dates array makes it a bit tricky to give exact answer :) but in the following example i assumed you have a well formatted string date, in which case you need to convert it back to the timestamp using same method (strtotime) before adding what you like into it .
$date = (new DateTime('now'))->format('Y-m-d H:i:s');
$new_date = date('Y-m-d H:i:s', strtotime('+4 hours', strtotime($date)));
echo $date . PHP_EOL . $new_date;
In other word, if your $date array contains UNIX time stamp then your original code should work
$date = (new DateTime('now'))->getTimestamp();
$new_date = date("Y-m-d H:i:s", strtotime('+4 hours', $date));