Check Array for Object with Same Key - php

Question

I'm creating an array of objects (or trying to) that looks like this:
Array
(
[1] => stdClass Object
(
[date] => 2016-09-28
)
[5] => stdClass Object
(
[date] => 2016-09-28
)
[2] => stdClass Object
(
[date] => 2016-09-29
)
[0] => stdClass Object
(
[date] => 2016-09-30
)
[4] => stdClass Object
(
[date] => 2016-09-30
)
[3] => stdClass Object
(
[date] => 2016-09-30
)
)
The trouble that I'm having is that I need can't work out how to check if an object with date->$date already exists.
I need an array of 'days' that I can then go on to add workshops to the corresponding days, not to a new object each time.
Can anyone make a suggestion?
EDIT
To put this in context, I'm iterating through a bunch of wordpress posts (of type 'workshop' in this case) which all have a piece of date meta. On my way through the loop I want to
Get the date(day)
Check if that date exists in the array
If not, add the date to the array
Then add the workshop object to that date array
What I should therefor end up with is an array containing three or four unique dates, each with an array of workshop objects.
Array(
Date 1(
Workshop(
Title, etc
),
Workshop()
)
Date 2(
Workshop(
Title, etc
)
Workshop()
)
)
My apologies, I'm sure my structure is off - this is a little advanced for me. Thanks for looking.

Answer 1

What you need is something like this. You can have a function to group your result.
function groupWorkShopsByDate($first_array){
$result_arr = array();
foreach( $first_array as $workShop ){
$result_arr[ $workShop->date ][] = $workShop;
}
return $result_arr;
}
Hope this helps!