为什么我仍然需要声明require_once('../config.php') in index.php？

Question

我有一个database.php，里面已经有require_once('../config.php')了。我不明白为什么我仍然需要把require_once('../config.php')和require_once('../database.php')都放在我的index.php中，而不是require_once('../database.php')，因为require_once('../config.php')已经在database.php中了？

如果我删除index.php中的require_once('../config.php')，我会出错。

<pre>Notice: Use of undefined constant DB_SERVER - assumed 'DB_SERVER' in C:xampphtdocslyndaphotoincludesdatabase.php on line 18
Notice: Use of undefined constant DB_USER - assumed 'DB_USER' in C:xampphtdocslyndaphotoincludesdatabase.php on line 18
Notice: Use of undefined constant DB_PASS - assumed 'DB_PASS' in C:xampphtdocslyndaphotoincludesdatabase.php on line 18
Warning: mysql_connect() [function.mysql-connect]: php_network_getaddresses: getaddrinfo failed: No such host is known. in C:xampphtdocslyndaphotoincludesdatabase.php on line 18
Warning: mysql_connect() [function.mysql-connect]: [2002] php_network_getaddresses: getaddrinfo failed: No such host is known. (trying to connect via tcp://DB_SERVER:3306) in C:xampphtdocslyndaphotoincludesdatabase.php on line 18
Warning: mysql_connect() [function.mysql-connect]: php_network_getaddresses: getaddrinfo failed: No such host is known. in C:xampphtdocslyndaphotoincludesdatabase.php on line 18</pre>
config.php
$server = "localhost";
$user = "root";
$db_pass = "password";
$db_name = "photo_gallery";
define("DB_SERVER", $server);
define("DB_USER", $user);
define("DB_PASS", $db_pass);
define("DB_NAME", $db_name);

database.php
require_once("config.php");
class MySQLDatabase {

private $connection;    
function __construct() {
$this->open_connection();
}
public function open_connection() {
$this->connection = mysql_connect(DB_SERVER, DB_USER, DB_PASS);
if (!$this->connection) {
die("Database connection failed: " . mysql_error());
}else {
$db_select = mysql_select_db(DB_NAME, $this->connection);
if (!$db_select) {
die("Database selection failed: " . mysql_error());
}
}
}
public function close_connection() {
if(isset($this->connection)) {
mysql_close($this->connection);
unset($this->connection);
}
}
}
$database = new MySQLDatabase();
$db =& $database;

这两个文件都在"localhost/photoglery/includes/"上提前感谢！：)

Answer 1

代码中的所有包含都基于index.php(或运行脚本)，因此require_once("config.php")将在index.php的同一目录上搜索文件。在database.php上尝试以下操作：

require_once(dirname(__FILE__) . "/config.php");

Answer 2

处理include文件的另一种方法是创建一个名为includes.php的文件。它将包含所有其他资源。

// Filename: includes.php
require_once 'database.php';
require_once 'config.php';

然后，在index.php和其他文档中，您可以通过包含该include文件来访问应用程序的所有资源。

require_once 'includes.php';