获取 caldav 对象的值

如何解决获取 caldav 对象的值

我有一组 caldav 对象（$events） 这里有一小部分：

Array
(
    [0] => CalDAVObject Object
        (
            [href:CalDAVObject:private] => localhost/caldav.PHP/[e-mail]
            [data:CalDAVObject:private] => BEGIN:VCALENDAR
PRODID:-//Synology//EN
VERSION:2.0
BEGIN:VEVENT
CREATED:20210426T182837
LAST-MODIFIED:20210426T182837
DTSTAMP:20210426T182837
UID:20210426T182837-82d4a110@192.168.109.1
SEQUENCE:6
SUMMARY:Test 1
TRANSP:OPAQUE
DTSTART;TZID=Europe/Amsterdam:20210427T130000
DTEND;TZID=Europe/Amsterdam:20210427T140000
DESCRIPTION:Test
LOCATION:
END:VEVENT
BEGIN:VTIMEZONE
TZID:Europe/Amsterdam
TZURL:http://tzurl.org/zoneinfo/Europe/Amsterdam
X-LIC-LOCATION:Europe/Amsterdam
LAST-MODIFIED:20160904T031233Z
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:19810329T020000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19961027T030000
RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
END:STANDARD
BEGIN:STANDARD
TZOFFSETFROM:+001932
TZOFFSETTO:+001932
TZNAME:AMT
DTSTART:18350101T000000
RDATE:18350101T000000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:+001932
TZOFFSETTO:+011932
TZNAME:NST
DTSTART:19160501T000000
RDATE:19160501T000000
RDATE:19170416T020000
RDATE:19180401T020000
RDATE:19190407T020000
RDATE:19200405T020000
RDATE:19210404T020000
RDATE:19220326T020000
RDATE:19230601T020000
RDATE:19240330T020000
RDATE:19250605T020000
RDATE:19260515T020000
RDATE:19270515T020000
RDATE:19280515T020000
RDATE:19290515T020000
RDATE:19300515T020000
RDATE:19310515T020000
RDATE:19320522T020000
RDATE:19330515T020000
RDATE:19340515T020000
RDATE:19350515T020000
RDATE:19360515T020000
RDATE:19370522T020000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+011932
TZOFFSETTO:+001932
TZNAME:AMT
DTSTART:19161001T000000
RDATE:19161001T000000
RDATE:19170917T030000
RDATE:19180930T030000
RDATE:19190929T030000
RDATE:19200927T030000
RDATE:19210926T030000
RDATE:19221008T030000
RDATE:19231007T030000
RDATE:19241005T030000
RDATE:19251004T030000
RDATE:19261003T030000
RDATE:19271002T030000
RDATE:19281007T030000
RDATE:19291006T030000
RDATE:19301005T030000
RDATE:19311004T030000
RDATE:19321002T030000
RDATE:19331008T030000
RDATE:19341007T030000
RDATE:19351006T030000
RDATE:19361004T030000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:+011932
TZOFFSETTO:+0120
TZNAME:nesT
DTSTART:19370701T000000
RDATE:19370701T000000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0120
TZOFFSETTO:+0020
TZNAME:NET
DTSTART:19371003T030000
RDATE:19371003T030000
RDATE:19381002T030000
RDATE:19391008T030000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:+0020
TZOFFSETTO:+0120
TZNAME:nesT
DTSTART:19380515T020000
RDATE:19380515T020000
RDATE:19390515T020000
END:DAYLIGHT
BEGIN:DAYLIGHT
TZOFFSETFROM:+0020
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:19400516T000000
RDATE:19400516T000000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19421102T030000
RDATE:19421102T030000
RDATE:19431004T030000
RDATE:19441002T030000
RDATE:19450916T030000
RDATE:19770925T030000
RDATE:19781001T030000
RDATE:19790930T030000
RDATE:19800928T030000
RDATE:19810927T030000
RDATE:19820926T030000
RDATE:19830925T030000
RDATE:19840930T030000
RDATE:19850929T030000
RDATE:19860928T030000
RDATE:19870927T030000
RDATE:19880925T030000
RDATE:19890924T030000
RDATE:19900930T030000
RDATE:19910929T030000
RDATE:19920927T030000
RDATE:19930926T030000
RDATE:19940925T030000
RDATE:19950924T030000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:19430329T020000
RDATE:19430329T020000
RDATE:19440403T020000
RDATE:19450402T020000
RDATE:19770403T020000
RDATE:19780402T020000
RDATE:19790401T020000
RDATE:19800406T020000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0100
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19770101T000000
RDATE:19770101T000000
END:STANDARD
END:VTIMEZONE
END:VCALENDAR
            [etag:CalDAVObject:private] => vlbdfylxugmiiywurxduuauhanffqjli
        )

如何获取“DTSTART”的值？