setTime() : sets the time in a DateTime object by specifying hours, minutes, and optionally seconds and microseconds

setTime( Hour, minutes, seconds )

date_default_timezone_set('America/Chicago');
$date = new DateTime('2012-04-15 22:15:40');
echo $date->format('Y/m/d H:i:s') . "<br>";
$date->setTime(23,30);
echo $date->format('Y/m/d H:i:s') . "<br>";

2012/04/15 22:15:40
2012/04/15 23:30:00

$date->setTime(2,50,32);

2012/04/15 22:15:40
2012/04/15 02:50:32

Procedural style

$date = date_create('2020-08-16');
date_time_set($date, 24, 56,58);
echo date_format($date, 'Y-m-d H:i:s');

2020-08-17 00:56:58

Using today's date

$date = new DateTime();
$date->setTime(14,30,45, 500000); //2:30:45 PM and 500000 microseconds
echo $date->format('Y-m-d  H:i:s.u'); // Output: 14:30:45.500000

2025-01-19  14:30:45.500000

Using Today's date and current time

$date = new DateTime(); // Current date and time
$currentHour = (int) $date->format('H');
$currentMinute = (int) $date->format('i');
$currentSecond = (int) $date->format('s');
$currentMicrosecond = (int) $date->format('u');

$date->setTime($currentHour, $currentMinute, $currentSecond, $currentMicrosecond);
echo $date->format('Y-m-d H:i:s.u'); // Output includes current date with precise time

2025-01-19 01:48:29.899328