URI提供了很多帮你对uri_string分段分割的方法，你可以很轻松的得到uri中某一段。如：

$this->uri->segment(n)

$this->uri->rsegment(n)

$this->uri->slash_segment(n)

$this->uri->slash_rsegment(n)

$this->uri->uri_to_assoc(n)

$this->uri->ruri_to_assoc(n)

等等。

/**

* 解析uri，确定路由

*/

class CI_URI {

//缓存uri片段

var$keyval= array();

//当前的uri片段

var $uri_string;

//URI片段数组 数组键值从0开始

var $segments= array();

//重建索引的片段数组 数组键值从1开始

var $rsegments= array();

//构造函数，需要获取config文件中的配置

function __construct()

{

$this->config =& load_class('Config', 'core');

log_message('debug', "URI Class Initialized");

}

//获取uri_string

function _fetch_uri_string()

{

//$this->config->item('uri_protocol')是获取config.php中uri_protocol的配置，AUTO为默认

if (strtoupper($this->config->item('uri_protocol')) == 'AUTO')

{

// 命令行方式执行

if (php_sapi_name() == 'cli' or defined('STDIN'))

{

$this->_set_uri_string($this->_parse_cli_args());

return;

}

// REQUEST_URI方式，绝大部分情况都能获取

if ($uri = $this->_detect_uri())

{

$this->_set_uri_string($uri);

return;

}

// PATH_INFO方式

$path = (isset($_SERVER['PATH_INFO'])) ? $_SERVER['PATH_INFO'] : @getenv('PATH_INFO');

if (trim($path, '/') != '' && $path != "/".SELF)

{

$this->_set_uri_string($path);

return;

}

// QUERY_STRING方式

$path = (isset($_SERVER['QUERY_STRING'])) ? $_SERVER['QUERY_STRING'] : @getenv('QUERY_STRING');

if (trim($path, '/') != '')

{

$this->_set_uri_string($path);

return;

}

// 尝试最后一种方式，通过$_GET获取键名

if (is_array($_GET) && count($_GET) == 1 && trim(key($_GET), '/') != '')

{

$this->_set_uri_string(key($_GET));

return;

}

// 如果还没获取到uri_string ,只能返回空了

$this->uri_string = '';

return;

}

//其实下面很多都是把上面的东西重写了，这是根据用户在config.php中配置的

$uri = strtoupper($this->config->item('uri_protocol'));

//若为REQUEST_URI方式

if ($uri == 'REQUEST_URI')

{

$this->_set_uri_string($this->_detect_uri());

return;

}

elseif ($uri == 'CLI')

{

$this->_set_uri_string($this->_parse_cli_args());

return;

}

$path = (isset($_SERVER[$uri])) ? $_SERVER[$uri] : @getenv($uri);

$this->_set_uri_string($path);

}

// --------------------------------------------------------------------

//就是给uri_string赋值

function _set_uri_string($str)

{

// 防止在ASCII字符之间插入空字符，如Java\0script.

$str = remove_invisible_characters($str, FALSE);

// If the URI contains only a slash we'll kill it

$this->uri_string = ($str == '/') ? '' : $str;

}

// --------------------------------------------------------------------

//检测URI

private function _detect_uri()

{

//$_SERVER['REQUEST_URI']和$_SERVER['SCRIPT_NAME']两者都存在才可使用

if ( ! isset($_SERVER['REQUEST_URI']) OR ! isset($_SERVER['SCRIPT_NAME']))

{

return '';

}

$uri = $_SERVER['REQUEST_URI'];

//去掉相同的部分，剩下有用的uri部分

if (strpos($uri, $_SERVER['SCRIPT_NAME']) === 0)

{

$uri = substr($uri, strlen($_SERVER['SCRIPT_NAME']));

}

elseif (strpos($uri, dirname($_SERVER['SCRIPT_NAME'])) === 0)

{

$uri = substr($uri, strlen(dirname($_SERVER['SCRIPT_NAME'])));

}

//允许?/welcome/index这种格式

if (strncmp($uri, '?/', 2) === 0)

{

$uri = substr($uri, 2);

}

$parts = preg_split('#\?#i', $uri, 2);

$uri = $parts[0];

if (isset($parts[1]))

{

$_SERVER['QUERY_STRING'] = $parts[1];

parse_str($_SERVER['QUERY_STRING'], $_GET);

}

else

{

$_SERVER['QUERY_STRING'] = '';

$_GET = array();

}

if ($uri == '/' || empty($uri))

{

return '/';

}

$uri = parse_url($uri, PHP_URL_PATH);

//做最后的处理返回uri

return str_replace(array('//', '../'), '/', trim($uri, '/'));

}

// --------------------------------------------------------------------

//解析命令行方式参数

private function _parse_cli_args()

{

$args = array_slice($_SERVER['argv'], 1);

return $args ? '/' . implode('/', $args) : '';

}

// --------------------------------------------------------------------

//过滤不合法的url字符，允许的uri是你的配置$config['permitted_uri_chars'] = 'a-z 0-9~%.:_\-';

function _filter_uri($str)

{

if ($str != '' && $this->config->item('permitted_uri_chars') != '' && $this->config->item('enable_query_strings') == FALSE)

{

if ( ! preg_match("|^[".str_replace(array('\\-', '\-'), '-', preg_quote($this->config->item('permitted_uri_chars'), '-'))."]+$|i", $str))

{

show_error('The URI you submitted has disallowed characters.', 400);

}

}

// Convert programatic characters to entities

$bad= array('$','(',')','%28','%29');

$good= array('$','(',')','(',')');

return str_replace($bad, $good, $str);

}

// --------------------------------------------------------------------

//如果你配置了url_suffix，则去掉

function _remove_url_suffix()

{

if ($this->config->item('url_suffix') != "")

{

$this->uri_string = preg_replace("|".preg_quote($this->config->item('url_suffix'))."$|", "", $this->uri_string);

}

}

// --------------------------------------------------------------------

//用/分隔uri_string,将结果保存到segments中

function _explode_segments()

{

foreach (explode("/", preg_replace("|/*(.+?)/*$|", "\\1", $this->uri_string)) as $val)

{

// Filter segments for security

$val = trim($this->_filter_uri($val));

if ($val != '')

{

$this->segments[] = $val;

}

}

}

//这个是重建索引，将数组从下标1开始，这是为了你的使用习惯，如$this->uri->segment(1)就是获取第一段

function _reindex_segments()

{

array_unshift($this->segments, NULL);

array_unshift($this->rsegments, NULL);

unset($this->segments[0]);

unset($this->rsegments[0]);

}

// --------------------------------------------------------------------

//获取uri中的一个片段

function segment($n, $no_result = FALSE)

{

return ( ! isset($this->segments[$n])) ? $no_result : $this->segments[$n];

}

// --------------------------------------------------------------------

//返回确定路由后的一个uri片段

function rsegment($n, $no_result = FALSE)

{

return ( ! isset($this->rsegments[$n])) ? $no_result : $this->rsegments[$n];

}

function uri_to_assoc($n = 3, $default = array())

{

return $this->_uri_to_assoc($n, $default, 'segment');

}

function ruri_to_assoc($n = 3, $default = array())

{

return $this->_uri_to_assoc($n, $default, 'rsegment');

}

function _uri_to_assoc($n = 3, $default = array(), $which = 'segment')

{

if ($which == 'segment')

{

$total_segments = 'total_segments';

$segment_array = 'segment_array';

}

else

{

$total_segments = 'total_rsegments';

$segment_array = 'rsegment_array';

}

if ( ! is_numeric($n))

{

return $default;

}

if (isset($this->keyval[$n]))

{

return $this->keyval[$n];

}

if ($this->$total_segments() < $n)

{

if (count($default) == 0)

{

return array();

}

$retval = array();

foreach ($default as $val)

{

$retval[$val] = FALSE;

}

return $retval;

}

$segments = array_slice($this->$segment_array(), ($n - 1));

$i = 0;

$lastval = '';

$retval = array();

foreach ($segments as $seg)

{

if ($i % 2)

{

$retval[$lastval] = $seg;

}

else

{

$retval[$seg] = FALSE;

$lastval = $seg;

}

$i++;

}

if (count($default) > 0)

{

foreach ($default as $val)

{

if ( ! array_key_exists($val, $retval))

{

$retval[$val] = FALSE;

}

}

}

// Cache the array for reuse

$this->keyval[$n] = $retval;

return $retval;

}

//很明显，它是将数组中的信息翻转成uri_string

function assoc_to_uri($array)

{

$temp = array();

foreach ((array)$array as $key => $val)

{

$temp[] = $key;

$temp[] = $val;

}

return implode('/', $temp);

}

//通过第二个参数看是否给uri前后加上“/”线

function slash_segment($n, $where = 'trailing')

{

return $this->_slash_segment($n, $where, 'segment');

}

function slash_rsegment($n, $where = 'trailing')

{

return $this->_slash_segment($n, $where, 'rsegment');

}

function _slash_segment($n, $where = 'trailing', $which = 'segment')

{

$leading= '/';

$trailing= '/';

if ($where == 'trailing')

{

$leading= '';

}

elseif ($where == 'leading')

{

$trailing= '';

}

return $leading.$this->$which($n).$trailing;

}

// --------------------------------------------------------------------

//返回uri片段数组

function segment_array()

{

return $this->segments;

}

function rsegment_array()

{

return $this->rsegments;

}

//计算uri片段的个数

function total_segments()

{

return count($this->segments);

}

function total_rsegments()

{

return count($this->rsegments);

}

// --------------------------------------------------------------------

//返回uri_string

function uri_string()

{

return $this->uri_string;

}

function ruri_string()

{

return '/'.implode('/', $this->rsegment_array());

}

}

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