Doctrine ArrayCollection fixed size

Doctrine ArrayCollection fixed size

I'm working with a database with an entity of type Store. Each store has
opening hours for each day of the week defined in an OpeningHour entity. A
store can only have a maximum of 7 OpeningHour entities. This is fine
since I can control that in the business logic.
However, the opening hours for a store may or may not be defined
explicitly. This means that when I update the opening hours I first need
to check if there are opening hours for that specific day already defined.
If they exist I need to update otherwise I need to add a new OpeningHour
entity to the ArrayCollection.
To get the opening hours for a store I do the following:
$openingHours = $store->getOpeningHours();
The $openingHours variable should now have a collection of not more than 7
entities (but might be less).
To update the opening hours I have a simple data structure that looks
something like this:
$values = array(
array(
'day' => "Monday",
'start' => "00:00:00",
'end' => "00:00:00",
)
);
The $values data structure can have up to 7 entries for each of the 7
days. My OpeningHour entity has the same properties as this data
structure.
My question is, how can I easily check within the $openingHours ollection
if a entity with a specific day name already exist?