php幻术方法： _get() 和 _set()的妙用

<?phpclass Post {  private $title;  private $content;  private $author;  private $comments;  private $_getters = array('title', 'content', 'author', 'comments');  private $_setters = array('title', 'content', 'author');    public function __get($property) {    if (in_array($property, $this->_setters)) {      return $this->$property;    }    else if (method_exists($this, '_get_' . $property))      return call_user_func(array($this, '_get_' . $property));    else if (in_array($property, $this->_getters) OR method_exists($this, '_set_' . $property))      throw new Exception('Property "' . $property . '" is write-only.');    else      throw new Exception('Property "' . $property . '" is not accessible.');  }  public function __set($property, $value) {    if (in_array($property, $this->_getters)) {      $this->$property = $value;    }    else if (method_exists($this, '_set_' . $property))      call_user_func(array($this, '_set_' . $property), $value);    else if (in_array($property, $this->_setters) OR method_exists($this, '_get_' . $property))      throw new Exception('Property "' . $property . '" is read-only.');    else      throw new Exception('Property "' . $property . '" is not accessible.');  }}?>This way the variables in the $_getters array can be read from the outside and the variables in the $_setters array can be modified from the outside, like this:<?php$post = new Post();$post->title = 'Hello, World';echo $post->title;// The following will throw an exception since $comments is read-only:$post->comments = 23;?>And in case you need a less generic getter or setter at some point, you can remove the variable from the $_getters or $_setters array and implement a method like:<?phpprivate function _set_title($value) {  $this->title = str_replace('World', 'Universe', $value);}?>And from the outside the property could still be used with:<?php$post->title = 'Hello, World!';?>