SassScriptFunction::perform PHP Method

    public function perform()
    {
        self::$context = new SassContext(SassScriptParser::$context);
        $name = preg_replace('/[^a-z0-9_]/', '_', strtolower($this->name));
        $args = $this->process_arguments($this->args);
        foreach ($this->args as $k => $v) {
            if (!is_numeric($k)) {
                self::$context->setVariable($k, $v);
            }
        }
        try {
            if (SassScriptParser::$context->hasFunction($this->name)) {
                $return = SassScriptParser::$context->getFunction($this->name)->execute(SassScriptParser::$context, $this->args);
                return $return;
            } elseif (SassScriptParser::$context->hasFunction($name)) {
                $return = SassScriptParser::$context->getFunction($name)->execute(SassScriptParser::$context, $this->args);
                return $return;
            }
        } catch (Exception $e) {
            throw $e;
        }
        if (isset(SassParser::$functions) && count(SassParser::$functions)) {
            foreach (SassParser::$functions as $fn => $callback) {
                if (($fn == $name || $fn == $this->name) && is_callable($callback)) {
                    $result = call_user_func_array($callback, $args);
                    if (!is_object($result)) {
                        $lexed = SassScriptLexer::$instance->lex($result, self::$context);
                        if (count($lexed) === 1) {
                            return $lexed[0];
                        }
                        return new SassString(implode('', $this->process_arguments($lexed)));
                    }
                    return $result;
                }
            }
        }
        if (method_exists('SassScriptFunctions', $name) || method_exists('SassScriptFunctions', $name = '_' . $name)) {
            $sig = self::get_reflection(array('SassScriptFunctions', $name));
            list($args) = self::fill_parameters($sig, $this->args, SassScriptParser::$context, $this);
            return call_user_func_array(array('SassScriptFunctions', $name), $args);
        }
        foreach ($this->args as $i => $arg) {
            if (is_object($arg) && isset($arg->quote)) {
                $args[$i] = (string) $arg;
            }
            if (!is_numeric($i) && SassScriptParser::$context->hasVariable($i)) {
                $args[$i] = SassScriptParser::$context->getVariable($i);
            }
        }
        // CSS function: create a SassString that will emit the function into the CSS
        return new SassString($this->name . '(' . join(', ', $args) . ')');
    }