简单工厂模式

public interface Operation{
    /*
    * 获取结果
    */
    public function get();
}

/*
*  加法类
*/
class OperationAdd implements Operation{
    private $_NumA;
    private $_NumB;
    
    public function __construct($num1,$num2) {
        $this->_NumA = $num1;
        $this->_NumB = $num2;
    }
    
    public function get() {
        return ($this->_NumA + $this->_NumB);
    }
}

class OperationSub implments Operation {
    private $_NumA;
    private $_NumB;
    
    public function __construct($num1,$num2) {
        $this->_NumA = $num1;
        $this->_NumB = $num2;
    }
    
    public function get() {
        return ($this->_NumA - $this->_NumB);
    }    
    
}

public class OperaFactory{
    
    private $_results;
    private $_opera;
    
    public function __construct() {
        $this->_results = 0;
    }
    
    public function Calculate($num1,$num2,$operator) {
        swtich($operator) {
            case '+':
                $this->_opera = new OperationAdd($num1,$num2);
                break;
            case '-':
                $this->_opera = new OperationSub($num1,$num2);
                break;
            default:
                break;
        }
        $this->_results = $this->_opera->get();
        return $this->_results;
    }   
}