get_elapsed_time()

<?php
/*********************************************************************
* get_elapsed_time.php
*
* Author: Steve Werby <steve at(@) befriend dot(.) com>
* Created: 2001-01-10 17:00
* Revised: 2001-01-10 17:45
*
* Purpose: Calculates elapsed time between two dates in MySQL
           DATETIME format, with formatting options (units, decimals)
           for output. 
*
* Latest version always available at http://www.befriend.com/.
*********************************************************************/

/*********************************************************************
* get_mysql_to_epoch() - converts MySQL datetime to epoch time in
* seconds.
*********************************************************************/

function get_mysql_to_epoch( $date )
{ 
    list( $year, $month, $day, $hour, $minute, $second )
        = split( '([^0-9])', $date );
    return date( 'U', mktime( $hour, $minute, $second, $month, $day,
        $year ) ); 
}

/*********************************************************************
* get_elapsed_time() - difference b/w start and end time in desired
* units.
*********************************************************************/

function get_elapsed_time( $time_start, $time_end,
    $units = 'seconds', $decimals = 2 )
{
    $divider['years']   = ( 60 * 60 * 24 * 365 );
    $divider['months']  = ( 60 * 60 * 24 * 365 / 12 );
    $divider['weeks']   = ( 60 * 60 * 24 / 7 );
    $divider['days']    = ( 60 * 60 * 24 );
    $divider['hours']   = ( 60 * 60 );
    $divider['minutes'] = ( 60 );
    $divider['seconds'] = 1;

    $elapsed_time = ( ( get_mysql_to_epoch( $time_end )
                    - get_mysql_to_epoch( $time_start ) ) 
                    / $divider[$units] );
    $elapsed_time = sprintf( "%0.{$decimals}f", $elapsed_time );

    return $elapsed_time;
}

/*********************************************************************
* Usage.
*********************************************************************/

$time_in  = '2000-06-14 06:30:00';
$time_out = '2000-12-22 13:45:00';

// Full use of function.
echo '<br>Days: ';
echo get_elapsed_time( $time_in, $time_out, 'days', 3 );

// Use defaults for units and decimal places.
echo '<br>Seconds: ';
echo get_elapsed_time( $time_in, $time_out );
?>