List all files in a directory and their respective subdirectories recursively

scandir_all.php

<?php

/**
 * List all files in a directory and their respective subdirectories recursively.
 * 
 * @param string $directory 
 * @return null|Generator 
 */
function scandir_all(string $directory): ?Generator
{
    if (!is_dir($directory)) {
        return;
    }
    $files = scandir($directory);
    foreach ($files as $file) {
        if ($file === '.' || $file === '..') {
            continue;
        }
        $absolutePath = realpath($directory) . DIRECTORY_SEPARATOR . $file;
        if (is_dir($absolutePath)) {
            yield from scandir_all($absolutePath);
            continue;
        }
        yield $absolutePath;
    }
}