What are the limitations of using strftime for time calculations in PHP?

When using strftime for time calculations in PHP, one limitation is that it only works with formatted time strings and does not support direct arithmetic operations on time values. To overcome this limitation, you can convert the time strings to Unix timestamps using strtotime, perform the necessary calculations, and then convert the result back to a formatted time string using strftime.

// Convert time strings to Unix timestamps
$start_time = strtotime('10:00:00');
$end_time = strtotime('12:30:00');

// Calculate time difference in seconds
$time_diff = $end_time - $start_time;

// Convert time difference back to formatted time string
$hours = floor($time_diff / 3600);
$minutes = floor(($time_diff % 3600) / 60);
$seconds = $time_diff % 60;

echo strftime('%H:%M:%S', mktime($hours, $minutes, $seconds));