php 调节者模式（代码）

   <?php
    /**  
     * AbstractColleague.  
     */  
    interface Filter  
    {  
        public function filter($value);  
    }  
     
    /**  
     * Colleague. We decide in the implementation phase  
     * that Colleagues should not know the next Colleague  
     * in the chain, resorting to a Mediator to link them together.  
     * This choice succesfully avoids a base abstract class  
     * for Filters.  
     * Remember that this is an example: it is not only  
     * Chain of Responsibility that can be alternatively implemented  
     * as a Mediator.  
     */  
    class TrimFilter implements Filter  
    {  
         public function filter($value)  
         {  
             return trim($value,'/');  
         }  
    }

    /**  
     * Colleague.  
     */  
    class NullFilter implements Filter  
    {  
         public function filter($value)  
         {  
             return str_replace(" ",'a',$value);  
         }  
    }  
     
    /**  
     * Colleague.  
     */  
    class HtmlEntitiesFilter implements Filter  
    {  
         public function filter($value)  
         {  
             return htmlentities($value);  
         }  
    }

    /**  
     * The Mediator. We avoid referencing it from ConcreteColleagues  
     * and so the need for an interface. We leave the implementation  
     * of a bidirectional channel for the Observer pattern's example.  
     * This class responsibility is to store the value and coordinate  
     * filters computation when they have to be applied to the value.  
     * Filtering responsibilities are obviously a concern of  
     * the Colleagues, which are Filter implementations.  
     */  
    class InputElement  
    {  
        protected $_filters;  
        protected $_value;  
     
        public function addFilter(Filter $filter)  
        {  
            $this->_filters[] = $filter;  
            return $this;  
        }  
     
        public function setValue($value)  
        {  
            $this->_value = $this->_filter($value);  
        }  
     
        protected function _filter($value)  
        {  
            foreach ($this->_filters as $filter) {  
                $value = $filter->filter($value);  
            }  
            return $value;  
        }  
     
        public function getValue()  
        {  
            return $this->_value;  
        }  
    }  
     
    $input = new InputElement();  
    $input->addFilter(new NullFilter())  
          ->addFilter(new TrimFilter())  
          ->addFilter(new HtmlEntitiesFilter());  
    $input->setValue(' You should use the <h1>-<h6> tags for your headings./');  
    echo $input->getValue(), "\n";
    ?>