Functions in PHP8: New ways to play array_is_list()

PHP8 is the latest PHP version that breaks records for innovation. PHP8 has added many new features and functions, one of which is the new way to play the function array_is_list(). In this article, I will discuss new ways to use this function and explain the benefits it can bring to developers.

First, let us look at the basic usage of array_is_list(). It is a built-in PHP function used to determine whether the array is a "list" type. If all keys in an array are consecutive integers, it is a list. For example, the following array is a list:

$list = [1, 2, 3, 4, 5];

And the following array is not a list:

$not_list = [1, 2, 4 => 'apple', 5];

Because the array $not_list contains non-consecutive keys, among which there is between key 4 and key 5 A gap. This means that the array cannot be considered a list.

Now, let’s explore new uses of array_is_list(). array_is_list() in PHP8 can accept an extra parameter - a boolean value, $allow_string_keys. If the value of this parameter is true, the function still returns true even if the array contains non-contiguous keys. Here is an example that shows how to use this new feature:

$list_with_strings_keys = [1, 2, 'foo' => 'bar', 4, 5];

// old way
$is_list = (array_values($list_with_strings_keys) === $list_with_strings_keys);

// new way
$is_list_with_string_keys = array_is_list($list_with_strings_keys, true);

var_dump($is_list_with_string_keys); // true

As you can see, the function array_is_list() takes a second parameter $allow_string_keys = true, which means that the array can contain Strings and non-consecutive keys. However, there are other interesting things. If the keys are strings and they look like integers, the function will also treat them as consecutive keys. The following example demonstrates this situation:

$not_list_but_looks_like_one = ['1' => 'a', '2' => 'b', 3 => 'c'];

$is_actually_a_list = array_is_list($not_list_but_looks_like_one, true);

var_dump($is_actually_a_list); // true

In this example, both keys of the array $not_list_but_looks_like_one are strings that look like integers. However, since the second parameter is true, the function array_is_list() still treats them as consecutive keys and returns true.

The new usage of array_is_list() has been explained earlier, now let us discuss the benefits it can bring to developers. In our actual projects, we occasionally encounter situations where we need to check whether an array is a list type. For example, when working with data like CSV files, it's very common to parse them into lists and store them in arrays. In this case, using the array_is_list() function can be very convenient. Additionally, thanks to the new parameter $allow_string_keys, which defaults to false, the function will be more flexible and can be adapted to a wider range of use cases.

Overall, the new way to play the function array_is_list() in PHP8 is very meaningful. It expands the flexibility of the function and provides more options to PHP developers. If you haven't tried PHP8 yet, I encourage you to use it as soon as possible and experience its new features.

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