I have an array that’s basically a simple collection of objects.
So
[obj1,obj2,obj3]
All instances of the same class. I then want to perform a map or filter to group these by a value in those objects.
$userIds = array_map(function($obj){
return = $obj->getUserId();
}, $objs);
And what I want is a result like this, where all the objects are sorted by their user ids:
[
'user1' => [$obj1],
'user2' => [$obj2, $obj4, $obj6],
'user3' => [$obj3, $obj5],
]
Looking for a way to do this cleanly with array functions to avoid a messy foreach and overwriting a variable. I have a few ideas but knowing PHP there’s probably a standard function that does it.
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Answer
array_map()
won’t allow you to declare the keys as you iterate.
array_reduce()
is an appropriate function for this task; it is also indicative of the fact that the first level in the output array will likely have a smaller count than the original array.
$objsByUserId = array_reduce(
$objs,
function($result, $obj) {
$result[$obj->getUserId()][] = $obj;
return $result;
},
[]
);
This will iterate all rows in $objs
and push each encountered object as a new element in a group based on the returned userId.