⏰ PHP date_time_set() Function

? Quick Overview

The date_time_set() function in PHP allows you to modify the time portion of an existing DateTime object by setting hours, minutes, seconds, and optional microseconds.

? Key Concepts

date_time_set() works only with DateTime objects
It changes time without affecting the date
Invalid time values (e.g., 25 hours) are auto-adjusted by PHP (rolling over to the next day)

? Syntax & Theory

This function directly updates the internal time of a DateTime instance.

Syntax:

date_time_set(DateTime $object, int $hour, int $minute, int $second = 0, int $microsecond = 0)

? Code Example

? View Code Example

// Create a DateTime object and update its time
<?php
$datetime = new DateTime("2025-07-18 12:30:00");

// Setting time to 15:45:00
date_time_set($datetime, 15, 45, 0);

echo $datetime->format('Y-m-d H:i:s');
?>

? Live Output / Explanation

The original time 12:30:00 is updated to 15:45:00 while keeping the date unchanged (2025-07-18). The formatted output confirms the updated time.

? Interactive Understanding

Think of DateTime as a clock attached to a calendar. The date_time_set() function adjusts only the clock hands without touching the calendar date.

? Use Cases

Scheduling tasks at a fixed time
Normalizing timestamps in applications
Adjusting user-provided time inputs

✅ Tips & Best Practices

Always validate your DateTime object before modification
Use format() to confirm changes visually
Prefer DateTime (OOP style) over legacy procedural date functions

? Try It Yourself

Create a DateTime object for today and set time to 08:00:00
Set the current time dynamically using date() values
Experiment with microseconds in date_time_set()