(PHP 5 >= 5.3.0, PHP 7)
Represents a date interval.
A date interval stores either a fixed amount of time (in years, months, days, hours etc) or a relative time string in the format that DateTime's constructor supports.
Number of years.
Number of months.
Number of days.
Number of hours.
Number of minutes.
Number of seconds.
Number of microseconds, as a fraction of a second.
Is 1 if the interval represents a negative time period and 0 otherwise. See DateInterval::format().
       If the DateInterval object was created by
       DateTime::diff(), then this is the total number of
       days between the start and end dates. Otherwise,
       days will be FALSE.
      
       Before PHP 5.4.20/5.5.4 instead of FALSE you will receive -99999 upon
       accessing the property.
      
| 版本 | 说明 | 
|---|---|
| 7.1.0 | The f property was added. |