<?php   
class Settings {   
    var $_settings = array ();   
       
    function get($var) {   
        $var = explode ( '.', $var );      
        $result = $this->_settings;   
        foreach ( $var as $key ) {   
            if (! isset ( $result [$key] )) {   
                return false;   
            }          
            $result = $result [$key];   
        }          
        return $result;   
    }   
       
    function load() {   
        trigger_error ( 'Not yet implemented', E_USER_ERROR );   
    }   
}   
  
class Settings_PHP extends Settings {   
    function load($file) {   
        if (file_exists ( $file ) == false) {   
            return false;   
        }   
           
        // Include file   
        include ($file);   
        unset ( $file );   
           
        // Get declared variables   
        $vars = get_defined_vars ();   
           
        // Add to settings array   
        foreach ( $vars as $key => $val ) {   
            if ($key == 'this')   
                continue;              
            $this->_settings [$key] = $val;   
        }   
       
    }   
}   
  
class Settings_INI extends Settings {   
    function load($file) {   
        if (file_exists ( $file ) == false) {   
            return false;   
        }   
        $this->_settings = parse_ini_file ( $file, true );   
    }   
}   
  
class Settings_YAML extends Settings {   
    function load($file) {   
        if (file_exists ( $file ) == false) {   
            return false;   
        }   
           
        include ('spyc.php');   
        $this->_settings = Spyc::YAMLLoad ( $file );   
    }   
}   
  
class Settings_XML extends Settings {   
    function load($file) {   
        if (file_exists ( $file ) == false) {   
            return false;   
        }   
           
        include ('xmllib.php');   
        $xml = file_get_contents ( $file );   
        $data = XML_unserialize ( $xml );   
           
        $this->_settings = $data ['settings'];   
    }   
}   
?>   
 php

/**  
* 针对PHP的配置,如有配置文件  
*config.php  
<?php  
$db = array();  
 
// Enter your database name here:  
$db['name'] = 'test';  
 
// Enter the hostname of your MySQL server:  
$db['host'] = 'localhost';  
?>  
 
//具体调用:  
include ('settings.php'); //原始环境假设每个类为单独的一个类名.php文件  
// Load settings (PHP)  
$settings = new Settings_PHP;  
$settings->load('config.php');  
echo 'PHP: ' . $settings->get('db.host') . '';  
*  
*/  
 读取INI文件,主要用到parser_ini_file函数,该函数返回一个数组,如第二个参数为true时则返回多维数组

/**  
* ini例子:config.ini  
*   
[db]  
name = test  
host = localhost  
 
//调用例子:  
$settings = new Settings_INI;  
$settings->load('config.ini');  
echo 'INI: ' . $settings->get('db.host') . '';  
*/  
 读取XML文件,需要用到XML_PARSER，xmllib.php在http://hudeyong926.iteye.com/admin/blogs/836048

/**  
* XML例子:config.xml  
<?xml version="1.0" encoding="UTF-8"?>  
<settings>  
<db>  
    <name>test</name>  
    <host>localhost</host>  
</db>  
</settings>  
 
// Load settings (XML)  
$settings = New Settings_XML;  
$settings->load('config.xml');  
echo 'XML: ' . $settings->get('db.host') . '';  
*  
*/  
 读取YAML格式文件,使用YAML必须使用到SPYC这个库,相关链接在http://spyc.sourceforge.net/

/**  
YAML配置例子:config.yaml  
db:  
   name: test  
   host: localhost   
 
// Load settings (YAML)  
$settings = New Settings_YAML;  
$settings->load('config.yaml');  
echo 'YAML: ' . $settings->get('db.host') . '';  
*/  
1。ini有点过时？？

2。xml比较好，

3。yaml很好，但是毕竟没有标准化。

4。txt要自己组织格式，开放性不好。

5。类序列化。比较好，但是不熟悉的人使用比较麻烦！

6。php定义常量（你不用修改数据吗？）

所以：xml最好。