Calculate Moon Phase Data with PHP

While developing ParaDB, I wanted to be able to calculate the phase of the moon given an arbitrary date and time. The only PHP software I found for this was the moon-phase class available from phpclasses.org. In my tests, however, I found it to be a bit less accurate than an equivalent Perl module I had used in the past called Astro::MoonPhase. So, I went ahead and just translated the Perl module to PHP.

The PHP version can be downloaded here. Feel free to expand on it, or rewrite it as a PHP class. If you use it in anything interesting, please let me know :)


Usage

The PHP moonphase functions work much like their Perl counterparts. Below is sample code returning a number of variables. This should be pretty familiar to those who have used the Astro::MoonPhase module:

require( 'moonphase.inc.php' );

$date = '2008-05-05';
$time = '20:36:00';
$tzone = 'PST';

// Usage: $data = phase( seconds_since_1970 );
$moondata = phase(strtotime($date . ' ' . $time . ' ' . $tzone));

$MoonPhase = $moondata[0];
$MoonIllum = $moondata[1];
$MoonAge = $moondata[2];
$MoonDist = $moondata[3];
$MoonAng = $moondata[4];
$SunDist = $moondata[5];
$SunAng  = $moondata[6];

To add to this example, you could then translate the phase into an easy-to-read format:

$phase = 'Waxing';
if ( $MoonAge > SYNMONTH/2 )  {
$phase = 'Waning';
}
print "$phase\n";

You could even make this a bit more useful by using $MoonIllum:

// Convert $MoonIllum to percent and round to whole percent.
$MoonIllum = round( $MoonIllum, 2 );
$MoonIllum *= 100;
if ( $MoonIllum == 0 )  {
$phase = "New Moon";
}
if ( $MoonIllum == 100 )  {
$phase = "Full Moon";
}

print "Moon Phase: $phase\n";
print "Percent Illuminated: $MoonIllum%\n";

More information can also be found with the Astro::MoonPhase documentation.

moonphase.inc.php -- Moonphase Functions
moonphase.php -- Sample Code

That's it, enjoy :)

Update: This script is now available as a PHP class.