PHP: DateTime '-1 day' - php

Question

I want to get the date of yesterday of the current date in a specifc time zone.
I tried like this, but it is not working:
$date = new DateTime(NULL, new DateTimeZone('Pacific/Wake'));
$yesterday = $date->modify( '-1 day' );
$yesterday = $yesterday->format('Y-m-d');
I am still getting today's date.

Answer 1

This problem, according to the documentation for the modify() method, seems to entirely depend on which version of php you're using. In this case, method chaining(which is what you're attempting to do is called), is only available on php version 5.3.0 and up, according to the changelog on the previously linked docs.
That in mind, it explains why your code didn't work, and #Deryck's did. If you ever do upgrade your php version, or get your host to upgrade it, you could likely reduce those three lines to two:
$date = new DateTime(NULL, new DateTimeZone('Pacific/Wake'));
$date = $date->modify( '-1 day' )->format('Y-m-d');
Not much of an improvement, I realize, but there's your reason for why it failed to work.
Below are two of the methods I see of getting around this; one is creation of a class.. which seems like overkill to me unless this is apart of something grander... the other is a creation of a function. Both shove the extra lines into something that takes up less space, in a sense.
class DT {
private $now; //can be null
private $timezone; //DateTimeZone object
public function __construct($tz_str, $now = NULL) {
$this->now = $now;
$this->timezone = new DateTimeZone($tz_str);;
}
public function mod($mod,$format) {
$dt = new DateTime($this->now, $this->timezone);
$dt->modify($mod);
return $dt->format($format);
}
}
function mod_formatted_zone($tz_str, $mod, $format, $now = NULL) {
$timezone = new DateTimeZone($tz_str);
$dt = new DateTime($now,$timezone);
$dt->modify($mod);
return $dt->format($format);
}
The use of either is simple; in the case of the class, it'd be something like..
$dt = new DT('Pacific/Wake');
echo $dt->mod('-1 day', 'Y-m-d');
While in the case of the function, it'd simply be..
echo mod_formatted_zone('Pacific/Wake', '-1 day', 'Y-m-d');

Answer 2

Seems to work once you don't re-assign the $date variable unnecessarily. See below:
<?php
$date = new DateTime(NULL, new DateTimeZone('Pacific/Wake'));
$date->modify("-1 day");
$date = $date->format("Y-m-d");
// echo $date; // just in case you wanna echo - ya dig
?>
View demo
FYI:
Wake Island Time Zone (UTC+12:00)
Which means 1 day before is actually today (for me at least, on the western hemisphere).

Answer 3

I want to get the date of yesterday of the current date in a specifc time zone.
You can specify relative dates in the DateTime constructor. This will work for you:-
$yesterday = new DateTime('- 1 day', new DateTimeZone('Pacific/Wake'));
var_dump($yesterday);
Proof!.