By the way, for anyone reading this in the future, this question was solved in an issue on my Github repo, found here. I'll post the solution here any way, just in case someone comes across this and has a similar issue. Using my Garethp/php-ews
library, the solution is as follows
$start = new DateTime('8:01 AM');
$end = new DateTime('9:00 AM');
$createdItemIds = $calendar->createCalendarItems(array(
'Subject' => 'Test',
'Start' => $start->format('c'),
'End' => $end->format('c'),
'RequiredAttendees' => array(
array(
'Mailbox' => array(
'Name' => 'Person 1',
'EmailAddress' => 'first@email.com',
)
),
array (
'Mailbox' => array(
'Name' => 'Person 2',
'EmailAddress' => 'second@email.com'
)
)
)
), array('SendMeetingInvitations' => 'SendOnlyToAll'));