코드루덴스

* 현재시간 
https://www.php.net/manual/en/function.time.php
time()
date_create('now')



* 특정시간으로 설정
https://www.php.net/manual/en/function.mktime.php
mktime(시, 분, 초,  월, 일, 년);



* 시간 단위 분리하기(년월일시분초)
https://www.php.net/manual/en/function.getdate.php
$arrTime = getDate( time() );



//===============
* 숫자 -> 문자열
- MySql TIMESTAMP 형식의 문자열로 출력
https://www.php.net/manual/en/function.date.php
date('Y-m-d H:i:s', time());



* 문자열 -> 숫자
- MySql TIMESTAMP 형식 문자열을 숫자로 변경
$time = strtotime('2010-03-21 19:30:50');


//
https://www.php.net/manual/en/class.datetime.php
use DateTime;
...
$input = '2010-04-29 19:30:50';  
$obj = DateTime::createFromFormat('Y-m-d H:i:s', $input);
$time = $obj->getTimestamp();//시간 숫자
$date = $obj->format('Y-m-d H:i:s');//시간 문자열

//
$date = date_create_from_format('Y-m-d H:i:s', '2010-04-29 19:30:50');
echo date_format($date, 'Y-m-d');



//================
* 더하기
https://daveismyname.blog/quick-way-to-add-hours-and-minutes-with-php
//set timezone
//date_default_timezone_set('GMT');
$start = '2014-06-01 14:00:00';
//display the converted time
echo date('Y-m-d H:i',strtotime('+1 hour +20 minutes',strtotime($start)));//음수도 가능(빼기 효과)



https://www.php.net/manual/en/datetime.add.php
$dt = new DateTime('now');
$date = $dt->add(date_interval_create_from_date_string('10 days'))->format('Y-m-d H:i:s');
$date = $dt->add(date_interval_create_from_date_string('-10 days'))->format('Y-m-d H:i:s');//음수도 가능(빼기 효과)

//
$date = date_create('2000-01-01');
date_add($date, date_interval_create_from_date_string('10 days'));



//=============
* 빼기
$dt = new DateTime('now');
$date = $dt->sub(date_interval_create_from_date_string('10 days'))->format('Y-m-d H:i:s');

//
$date = date_create('2000-01-20');
date_sub($date, date_interval_create_from_date_string('10 days'));


//===============
* 차이 구하기
https://www.php.net/manual/en/datetime.diff.php
$datetime1 = new DateTime('2009-10-11');
$datetime2 = new DateTime('2009-10-13');
$interval = $datetime1->diff($datetime2);

//
$datetime1 = date_create('2009-10-11');
$datetime2 = date_create('2009-10-13');
$interval = date_diff($datetime1, $datetime2);