How does the gmmktime() function differ from the mktime() function in PHP, and what impact does this have on time calculations?

The gmmktime() function in PHP is similar to mktime() but it uses Greenwich Mean Time (GMT) instead of the local time zone. This difference can impact time calculations when dealing with time zones or daylight saving time changes. To ensure consistency in time calculations across different time zones, it's important to use gmmktime() when working with GMT-based calculations.

// Using gmmktime() instead of mktime() for GMT-based time calculations
$timestamp = gmmktime(12, 0, 0, 6, 15, 2021);
echo gmdate("Y-m-d H:i:s", $timestamp);