<?php

class read
{
    private $data;

    function __construct()
    {
        if ($db = new DataBase()) {
            $this->data = $db->showData();
        }
    }

    function __toString()
    {
        $out = '';
        while ($this->data) {
            $out .= '<tr>';
            $out .= "</td>'".$this->data["id"]."'</td>";
            $out .= "</td>'".$this->data["title"]."'</td>";
            $out .= "</td>'".$this->data["u_id"]."'</td>";
            $out .= "</td>'".$this->data["content"]."'</td>";
            $out .= "</td>'".$this->data["time"]."'</td>";
            $out .= '</tr>';
        }
        $out .= '</table></div>';
        return $out;
    }
}

这段代码哪里有问题吗？运行总是出错。