RecursiveArrayHelper

abstract class RecursiveArrayHelper {
    /**
     * @var string
     */
    static private $separator='.';

    /**
     * @param array $array
     * @param string $key
     * @return bool
     */
    static public function has(array $array, $key) {
        assert('is_scalar($key)');
        $keyParts = self::getKeyParts($key);
        return self::hasKeyParts($array, $keyParts);
    }

    /**
     * @param array $array
     * @param string $key
     * @param mixed $default
     * @return mixed
     */
    static public function get(array $array, $key, $default=null) {
        assert('is_scalar($key)');
        $keyParts = self::getKeyParts($key);
        return self::getByKeyParts($array, $keyParts, $default);
    }

    /**
     * @param array $array
     * @param string $key
     * @param mixed $value
     * @return array
     */
    static public function set(array $array, $key, $value) {
        assert('is_scalar($key)');
        $keyParts = self::getKeyParts($key);
        $array = self::setByKeyParts($array, $keyParts, $value);
        return $array;
    }

    /**
     * @return string
     */
    static public function getSeparator() {
        return self::$separator;
    }

    /**
     * @param string $separator
     * @return void
     */
    static public function setSeparator($separator) {
        assert('is_string($key) && strlen($separator)>0');
        self::$separator = $separator;
    }

    /**
     * @param array $array
     * @param array $keyParts
     * @return bool
     */
    static private function hasKeyParts(array $array, array $keyParts) {
        $currentKey = array_shift($keyParts);
        if(array_key_exists($currentKey, $array)) {
            if(!count($keyParts)) {
                return true;
            } else {
                return self::hasKeyParts($array[$currentKey], $keyParts);
            }
        }
        return false;
    }

    /**
     * @param array $array
     * @param array $keyParts
     * @param mixed $default
     * @return mixed
     */
    static private function getByKeyParts(array $array, array $keyParts, $default) {
        $currentKey = array_shift($keyParts);
        if(array_key_exists($currentKey, $array)) {
            if(!count($keyParts)) {
                return $array[$currentKey];
            } else {
                return self::getByKeyParts($array[$currentKey], $keyParts, $default);
            }
        }
        return $default;
    }

    /**
     * @param array $array
     * @param array $keyParts
     * @param mixed $value
     * @return array
     */
    static private function setByKeyParts(array $array, array $keyParts, $value) {
        $currentKey = array_shift($keyParts);
        if(!array_key_exists($currentKey, $array)) {
            $array[$currentKey] = array();
        }
        if(!count($keyParts)) {
            $array[$currentKey] = $value;
            return $array;
        }
        $array[$currentKey] = self::setByKeyParts($array[$currentKey], $keyParts, $value);
        return $array;
    }

    /**
     * @param string $key
     * @return array
     */
    static private function getKeyParts($key) {
        return explode(self::$separator, $key);
    }
}