Get number of days between two dates

<?php
/**
 * Calculating the difference between two dates
 * @author: Elliott White
 * @author: Jonathan D Eisenhamer.
 * @link: http://www.quepublishing.com/articles/article.asp?p=664657&rl=1
 * @since: Dec 1, 2006.
 */
 
if( function_exists( 'date_default_timezone_set' ) )
{
	// Set the default timezone to US/Eastern
	date_default_timezone_set( 'US/Eastern' );
}
 
// Will return the number of days between the two dates passed in
function count_days( $a, $b )
{
    // First we need to break these dates into their constituent parts:
    $gd_a = getdate( $a );
    $gd_b = getdate( $b );
 
    // Now recreate these timestamps, based upon noon on each day
    // The specific time doesn't matter but it must be the same each day
    $a_new = mktime( 12, 0, 0, $gd_a['mon'], $gd_a['mday'], $gd_a['year'] );
    $b_new = mktime( 12, 0, 0, $gd_b['mon'], $gd_b['mday'], $gd_b['year'] );
 
    // Subtract these two numbers and divide by the number of seconds in a
    //  day. Round the result since crossing over a daylight savings time
    //  barrier will cause this time to be off by an hour or two.
    return round( abs( $a_new - $b_new ) / 86400 );
}
 
// Prepare a few dates
$date1 = strtotime( '12/3/1973 8:13am' );
$date2 = strtotime( '1/15/1974 10:15pm' );
$date3 = strtotime( '2/14/2005 1:32pm' );
 
// Calculate the differences, they should be 43 & 11353
echo "<p>There are ", count_days( $date1, $date2 ), " days.</p>\n";
echo "<p>There are ", count_days( $date2, $date3 ), " days.</p>\n";
?>