src/shmop.php
protected function exists(int $id = 0): bool
    {
        return (bool)@shmop_open($id ? $id : $this->id, 'a', 0, 0);
    }
protected function exists(int $id = 0): bool
    {
        return (bool)@shmop_open($id ? $id : $this->id, 'a', 0, 0);
    }
protected function exists ( int $ id = 0 ) : bool { return ( bool ) @ shmop_open ( $ id ? $ id : $ this -> id , 'a' , 0 , 0 ) ; }
Whether there is a system's id
@param int $id [optional]
@return bool
Whether there is a system s id