策略模式

interface 
{
    public function doOperation($num1, $num2 );
}

class OperationAdd implements 
{
    public function doOperation($num1, $num2)
    {
        return $num1 + $num2;
    }
}

class OperationSubstract implements 
{
    function doOperation( $num1 , $num2 )
    {
        return $num1 - $num2;
    }
}

class OperationMultiply implements 
{
        public function doOperation( $num1 , $num2 )
        {
                return $num1 * $num2;
        }
}

class Context
{
   private $strategy;

   public function __construct($strategy){
       $this->strategy = $strategy;
   }

   public function executeStrategy($num1, $num2){
      return $this->strategy->doOperation($num1, $num2);
   }
}

$context = new Context(new OperationAdd());
echo ("10 + 5 = " . $context->executeStrategy(10, 5));
echo PHP_EOL;

$context = new Context(new OperationSubstract());
echo ("10 - 5 = " . $context->executeStrategy(10, 5));
echo PHP_EOL;

$context = new Context(new OperationMultiply());
echo ("10 * 5 = " . $context->executeStrategy(10, 5));
echo PHP_EOL;