In date_sun_info() what is Transit

Question

I understand the meaning of Sun Transit to be the time it takes for the sun to move from the sunrise position to the sunset position however date_sun_info() transit seems to return the midpoint in the day where the sun is exactly between the sunrise and sunset position.

$sun_info = date_sun_info(strtotime("2006-12-12"), 31.7667, 35.2333);
foreach ($sun_info as $key => $val) {
 echo "$key: " . date("H:i:s", $val) . "\n";
}

The above example will output:

sunrise: 05:52:11
sunset: 15:41:21
transit: 10:46:46
civil_twilight_begin: 05:24:08
civil_twilight_end: 16:09:24
nautical_twilight_begin: 04:52:25
nautical_twilight_end: 16:41:06
astronomical_twilight_begin: 04:21:32
astronomical_twilight_end: 17:12:00

Answer 1

Transit is the time that the sun passes over the observer's meridian. So it is midday by a sundial at the longitude you happen to be at. Clock midday and solar midday are often quite different and I suspect the time given is UTC, although that is a guess as it is not explained in the manual and I would expect this to give a result nearer to 12:00, although I haven't had time to check the calculation properly.

It may be that the person who wrote this function did not understand the term 'transit' just as the person who wrote the date_sunrise() and date_sunset() functions did not understand the term 'zenith'.