how do I subtract 24 hour from date time object in PHP

Question

I have the following code:

  $now = date(\"Y-m-d H:m:s\");
  $date = date(\"Y-m-d H:m:s\", strtotime(\'-24 hours\', $now));

However, now it

Answer 1

strtotime() expects a unix timestamp (which is number seconds since Jan 01 1970)

$date = date("Y-m-d H:i:s", strtotime('-24 hours', time())); ////time() is default so you do not need to specify.

i would suggest using the datetime library though, since it's a more object oriented approach.

$date = new DateTime(); //date & time of right now. (Like time())
$date->sub(new DateInterval('P1D')); //subtract period of 1 day

The advantage of this is that you can reuse the DateInterval:

$date = new DateTime(); //date & time of right now. (Like time())
$oneDayPeriod = new DateInterval('P1D'); //period of 1 day
$date->sub($oneDayPeriod);
$date->sub($oneDayPeriod); //2 days are subtracted.
$date2 = new DateTime(); 
$date2->sub($oneDayPeriod); //can use the same period, multiple times.

Carbon (update 2020)

Most popular library for processing DateTimes in PHP is Carbon.

Here you would simply do:

$yesterday = Carbon::now()->subDay();