PHP按钮返回404错误

".mysql_error()."

";    }        if(isset($_post['author']) &&       isset($_post['title']) &&       isset($_post['category']) &&       isset($_post['year']) &&       isset($_post['isbn']))        {            $author = get_post('author');            $title = get_post('title');            $category = get_post('category');            $year = get_post('year');            $isbn = get_post('isbn');                          $query = "INSERT INTO classics VALUES".              "('$author','$title','$category','$year','$isbn')";                            if(!mysql_query($query, $db_server))            {                echo "INSERT failed: $query
".mysql_error()."

";            }        }        echo <<<_END                _END;        $query = "SELECT * FROM classics";    $result = mysql_query($query);        if(!$result) die("Datebase access failed: ".mysql_error);        $rows = mysql_num_rows($result);        for($j = 0; $j<$rows; ++$j)    {        $row = mysql_fetch_row($result);            echo <<<_END        
               Author $row[0]                Title $row[1]             category $row[2]                 year $row[3]                 ISBN $row[4]        
                    _END;    }        mysql_close($db_server);        function get_post($var)    {            return mysql_real_escape_string($_POST[$var]);    }?>

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加断点一步一步调试。