Laravel 5 Collections: Filtering a Collection Based On Key Presence With whereIn

The whereIn method is used to filter the collection based on a given $key and an array of the possible $values that the $key can have. The method also defines an optional $strict parameter, which when an argument with a truth value of true is supplied, will cause the method to check the types of each item in the collection against the types in the supplied $values array ($strict is set to true by default). This method does not change the original Collection instance and will return a new, modified, Collection instance.

#Signature

1public function whereIn(
2    $key,
3    $values,
4    $strict = false
5);

#Example Use

The following examples will use the following collection to demonstrate the whereIn method:

1// Create a new collection.
2$people = collect([
3    ['name' => 'Alice', 'age' => 26],
4    ['name' => 'Bob',   'age' => 34],
5    ['name' => 'Chris', 'age' => 26]
6]);

We can quickly get a subset of the $people collection based on their age. Assuming we wanted to retrieve all people whose age was 26 we could use the whereIn method like so:

1$results = $people->whereIn('age', [26]);

After the above code has executed, the $results variable will contain a value similar to the following output:

 1Collection {
 2  #items: array [
 3    0 => array [
 4      "name" => "Alice"
 5      "age"  => 26
 6    ]
 7    2 => array [
 8      "name" => "Chris"
 9      "age"  => 26
10    ]
11  ]
12}

To see the effects of the $strict argument, we can change the above example only slightly to cause the method to return no results:

1// Notice that the value in the array is
2// a string, not an integer.
3$results = $people->whereIn('age', ['26']);

Because the age of each person in the $people array is an integer and the item in the $values array in the previous code example is a string, the $results variable would be an empty Collection instance. To get this to work, simply pass false as the argument for the $strict parameter:

1// Disable type checking by supplying an
2// argument that evaluates to false
3// for the $strict parameter.
4$results = $people->whereIn('age', ['26'], false);

After the above code has executed, the $results variable would the same items as in our first example (both Alice and Chris would be returned).

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