updating a datetime sql value by exactly a year - php

Question

im trying to get a datetime variable (example: 2019-02-10 03:13:33) to update exactly a year. i read that datetime is written as a string so i tried to subtract by itself and add +365.
the code works if i take out all "expirationdate" including the bind value. also for some reason, i have to keep my UPDATEs encased in single quotations because theres no changes in my database if they are inside double quotes.
$stmt = $db->prepare('UPDATE usr_customer_profile SET packageid = 3, expirationdate = .'$oneyear'. WHERE usrcustomerid = :usrcustomerid');
$stmt->bindValue(':expirationdate', $_SESSION['expirationdate'], PDO::PARAM_STR);
$stmt->bindValue(':usrcustomerid', $_SESSION['usrcustomerid'], PDO::PARAM_INT);
$oneyear = (':expirationdate' - ':expirationdate') + 365;
$stmt->execute();

Answer 1

You can do this in PHP or SQL. In PHP you can use strtotime or (preferably) the DateTime class to add one year to the value in $_SESSION['expirationdate']:
// using strtotime
$expirationdate = date('Y-m-d H:i:s', strtotime($_SESSION['expirationdate'] . ' + 1 year'));
// using DateTime
$expiration = new DateTime($_SESSION['expiration_date']);
$expiration->add(new DateInterval('P1Y'));
$expirationdate = $expiration->format('Y-m-d H:i:s');
// do the query
$stmt = $db->prepare('UPDATE usr_customer_profile
SET packageid = 3,
expirationdate = :expirationdate
WHERE usrcustomerid = :usrcustomerid');
$stmt->bindValue(':expirationdate', $expirationdate, PDO::PARAM_STR);
$stmt->bindValue(':usrcustomerid', $_SESSION['usrcustomerid'], PDO::PARAM_INT);
$oneyear = (':expirationdate' - ':expirationdate') + 365;
$stmt->execute();
In SQL use + INTERVAL 1 YEAR to add 1 year to the expiration date:
$stmt = $db->prepare('UPDATE usr_customer_profile
SET packageid = 3,
expirationdate = :expirationdate + INTERVAL 1 YEAR
WHERE usrcustomerid = :usrcustomerid');
$stmt->bindValue(':expirationdate', $_SESSION['expirationdate'], PDO::PARAM_STR);
$stmt->bindValue(':usrcustomerid', $_SESSION['usrcustomerid'], PDO::PARAM_INT);
$oneyear = (':expirationdate' - ':expirationdate') + 365;
$stmt->execute();