Get data from a directory and merge it into an array

app.php

// config/app.php
<?php

return [
  'app' => 'app_name',
  'url' => 'localhost:8080',
];

Config.php

<?php

namespace Core\Service;

class Config
{
    /**
     * @var string $directory
     * Directory
     */
    private static $directory = 'config';

    /**
     * @var $settings
     * All config in array
     */
    private static $settings;

    /**
     * @param string $key
     * @return string
     * Get value from config directory
     */
    public static function get($key)
    {
        if (is_null(self::$settings)) {
            self::$settings = self::merge_config();
        }
        return self::$settings[$key];
    }

    /**
     * @return array $result
     * merge all php files
     */
    protected static function merge_config()
    {
        $configs = glob(ROOT . DIRECTORY_SEPARATOR . self::$directory . DIRECTORY_SEPARATOR . '*.php');
        $result  = [];
        foreach ($configs as $conf) {
            $file = str_replace('.php', '' , explode(DIRECTORY_SEPARATOR, $conf)[sizeof(explode(DIRECTORY_SEPARATOR, $conf)) - 1]);
            $c = include $conf;
            array_walk($c, function ($v, $k) use (&$result, $file) {
                $result[$file . '.' . $k] = $v;
            });
        }
        return $result;
    }
}