Working on a new MVC Application Framework i use this method to check how many arguments are required before calling the sub method!

Example 

<?php
        $this->method_args_count = $this->CReflection
            ->getMethod($Route->getMethod())
            ->getNumberOfParameters();
        //Maybe be 5 but if uri is /controller/method/single_param/ we only of 1
        $this->params = $Route->getParams(); //0 in some cases

        if($this->method_args_count > count($this->params))
        {
            $this->difference = ($this->method_args_count - count($this->params));
            for($i=0;$i<=$this->difference;$i++)
            {
                $this->params[] = false;
            }
        }
        
        //Call the method with correct amount of params
        // but as false for params that have not been passed!
        call_user_func_array(array(new $this->obj,$Route->getMethod()),$this->params);
?>

$reflection = new ReflectionFunction('implode');
echo $reflection->getNumberOfParameters();