8 

     9     /**

    10      * convert DateIntervals to milliseconds

    11      * Months and year calculated by approximation based on average number

    12      * of days over 4 years (365*4+1)

    13      * @param \DateInterval $di the date interval

    14      * @return the number of milliseconds or 0 if $di is null

    15      */

    16     public static function dateIntervalToMillis(\DateInterval $di) {

    17         if(is_null($di)) {

    18             return 0;

    19         }

    20         $seconds = ($di->s)

    21          + ($di->i * 60)

    22          + ($di->h * 60 * 60)

    23          + ($di->d * 60 * 60 * 24)

    24          + ($di->m * (365*4+1)/48*60*60*24)

    25          + ($di->y * (365*4+1)/4*60*60*24);

    26         return $seconds*1000;

    27     }

    28 

    29     /**

    30      * convert iso8601 strings to milliseconds

    31      * Months and year calculated by approximation based on average number

    32      * of days over 4 years (365*4+1)

    33      *

    34      * @param str iso8601 string

    35      * @return the number of milliseconds or 0 if $str is null

    36      */

    37     public static function iso8601IntervalToMillis($str) {

    38         if(is_null($str) || $str === '') {

    39             return 0;

    40         }

    41         $di = new \DateInterval($str);

    42         return self::dateIntervalToMillis($di);

    43     }