What are the situations when PHP functions return array type data?

PHP functions may encounter the following situations when returning array type data: if the return array type is explicitly declared, the array will be returned directly; returning a null value will cause an error; calling a function that receives an array can return another array.

PHP function returns array type data

In PHP, when a function returns array type data, it usually encounters To the following situation:

1. Explicit array type hint

When the function signature explicitly declares that the returned data type is an array, the function will return an array. For example:

function get_data(): array
{
    return ['name' => 'John', 'age' => 30];
}

2. Return null

Some functions may return null values, for example when the required data cannot be found. However, when a function is declared to return an array type, returning null raises an error.

3. Call the function that receives the array

PHP also provides some functions (such as array_filter() and array_map() ), they receive an array as argument and return another array. The following example shows how to use the array_filter() function:

function filter_numbers(array $arr)
{
    return array_filter($arr, function($item) {
        return is_numeric($item);
    });
}

$numbers = [1, 2, 'a', 4, 'b'];
$result = filter_numbers($numbers);
// $result 现在是一个仅包含数字的数组

Practical case: Get a list of files

Consider a method to get a list of files in a specified directory Function:

function get_files(string $dir): array
{
    if (!is_dir($dir)) {
        throw new InvalidArgumentException("$dir is not a valid directory.");
    }

    $files = scandir($dir);
    if ($files === false) {
        throw new RuntimeException("Failed to scan directory.");
    }

    foreach ($files as $key => $file) {
        if ($file == '.' || $file == '..') {
            unset($files[$key]);
        }
    }

    return array_values($files);
}

This function returns an array containing the file names in the directory. It handles invalid directories, failed directory scans, and dereferences of the current directory and parent directories.

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