动态类变量答案

【问题标题】：Dynamic class variables动态类变量
【发布时间】：2008-09-19 12:18:11
【问题描述】：

PHP 有自动生成类变量的方法吗？我认为我以前见过类似的东西，但我不确定。

public class TestClass {
    private $data = array();

    public function TestClass() {
        $this->data['firstValue'] = "cheese";
    }
}

$this->data 数组始终是关联数组，但它们的键因类而异。有什么可行的方法可以从$this->firstValue 访问$this->data['firstValue'] 而无需定义链接？

如果是的话，有什么缺点吗？

或者如果$this->data 数组不包含该键，是否有一种静态方法来定义链接？

【问题讨论】：

标签： php oop

【解决方案1】：

请看这里：http://www.php.net/manual/en/language.oop5.overloading.php

你想要的是“__get”方法。链接上有一个您需要的示例。

【讨论】：

【解决方案2】：

使用 PHP5 “魔法”__get() 方法。它会像这样工作：

public class TestClass {
    private $data = array();

    // Since you're using PHP5, you should be using PHP5 style constructors.
    public function __construct() {
        $this->data['firstValue'] = "cheese";
    }

    /**
     * This is the magic get function.  Any class variable you try to access from 
     * outside the class that is not public will go through this method.  The variable
     * name will be passed in to the $param parameter.  For this example, all 
     * will be retrieved from the private $data array.  If the variable doesn't exist
     * in the array, then the method will return null.
     *
     * @param string $param Class variable name
     *
     * @return mixed
     */
    public function __get($param) {
        if (isset($this->data[$param])) {
            return $this->data[$param];
        } else {
            return null;
        }
    }

    /**
     * This is the "magic" isset method.  It is very important to implement this 
     * method when using __get to change or retrieve data members from private or 
     * protected members.  If it is not implemented, code that checks to see if a
     * particular variable has been set will fail even though you'll be able to 
     * retrieve a value for that variable.
     *
     * @param string $param Variable name to check
     * 
     * @return boolean
     */
    public function __isset($param) {
        return isset($this->data[$param]);
    }

    /**
     * This method is required if you want to be able to set variables from outside
     * your class without providing explicit setter options.  Similar to accessing
     * a variable using $foo = $object->firstValue, this method allows you to set 
     * the value of a variable (any variable in this case, but it can be limited 
     * by modifying this method) by doing something like:
     * $this->secondValue = 'foo';
     * 
     * @param string $param Class variable name to set
     * @param mixed  $value Value to set
     * 
     * @return null
     */
    public function __set($param, $value) {
        $this->data[$param] = $value;
    }
}

使用神奇的 __get、__set 和 __isset 构造函数，您可以控制在类上设置变量的方式，同时仍将所有值存储在单个数组中。

希望这会有所帮助:)

【讨论】：