public function A(){
        return "testA";
    }
    public function test(){
        $param = 'A';
        $test = $this->$param();
        return $test;
    }

public function A(){
            return "testA";
        }
        public function test(){
            $param = 'A';
            $test = $this->{$param}();
            return $test;
        }