PHP Dynamic Static Methods

<?php

class Dynamic {
    const RE_MethodName = '@[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*@';

    static protected $container = array();

    static public function attach ($name, $method) {
        if(!is_string($name))
            throw new \InvalidArgumentException('$name should be a string.');
        if(!preg_match(self::RE_MethodName, $name))
            throw new \InvalidArgumentException('$name is not a valid method name');
        if(!is_callable($method))
            throw new \InvalidArgumentException('$method should be callable.');

        self::$container[$name] = $method;
    }

    static public function __callStatic ($name, $arguments) {
        return isset(self::$container[$name])
            ? call_user_func_array(self::$container[$name], $arguments)
            : null;
    }

    protected function __construct () {}
}

Dynamic::attach('urlsafe', function ($value) {
    $value = strtolower($value);
    $value = preg_replace('@[^a-z0-9_#%:]+@', '-', $value);
    return trim($value, '-');
});

echo Dynamic::urlsafe('My precious URL + something else.');
echo Dynamic::does_not_exist('The ABC.');

// urlsafe        : my-precious-url-something-else
// does_not_exist :