php – 警告：缺少1个参数

知道我为什么会收到这个错误：

Warning: Missing argument 1 for person::__construct(),called in /home/fishbein/public_html/dev/OOP/index.PHP on line 5 and defined in /home/fishbein/public_html/dev/OOP/class_lib.PHP on line 6

Warning: Missing argument 1 for person::__construct(),called in /home/fishbein/public_html/dev/OOP/index.PHP on line 6 and defined in /home/fishbein/public_html/dev/OOP/class_lib.PHP on line 6

使用此代码：

<?
    class person {

            var $name;

            function __construct($persons_name) {       
            $this->name = $persons_name;        
            }

            function set_name($new_name) {
                $this->name = $new_name;
            }

            function get_name() {
                return $this->name;
            }

    }
?>

我也在我的索引文件中使用它：

$tyler = new person("Tyler");

实例化时你做了：$obj = new person();而不是$obj =新人(“乔”);