PHP strange DOCUMENT_ROOT

So basically, I'm writing a framework, and as part of it features, it's supposed to provide a set of well-established URIs/paths to the end-developer.

Some two of these paths make use of $_SERVER['DOCUMENT_ROOT']:

/**
 * Absolute filesystem path to web root install (aka docroot).
 * @example "C:/wamp/www" OR "/home/visitgoz/public_html/"
 */
CFG::set('ABS_WWW',
    str_replace(
        $tmpseps,
        DIRECTORY_SEPARATOR,
        truepath($_SERVER['DOCUMENT_ROOT']).'/'
    )
);

/**
 * K2F path relative to web root.
 * @example /K2F/
 */
CFG::set('REL_K2F',
    str_replace(
        array('//','\\'),
        '/',
        str_replace(CFG::get('ABS_WWW'),'/',CFG::get('ABS_K2F'))
    )
);

The code has been fine-tuned to work on both Linux and Windows. Apparently, it works most of the time on Linux, quite seamless in fact on VPSes.

However, as of late, I tried it on an HG Reseller Account (shared hosting) and it all broke up. I've printed out data inside $_SERVER on the problematic machine:

Array
(
**  [DOCUMENT_ROOT] => /usr/local/apache/htdocs
    [GATEWAY_INTERFACE] => CGI/1.1
    [HTTP_ACCEPT] => text/html,application/xhtml+xml,application/xml;q=0.9;q=0.8
    [HTTP_ACCEPT_CHARSET] => ISO-8859-1,utf-8;q=0.7,*;q=0.7
    [HTTP_ACCEPT_ENCODING] => gzip,deflate
    [HTTP_ACCEPT_LANGUAGE] => en-gb,en;q=0.5
    [HTTP_CONNECTION] => keep-alive
    [HTTP_COOKIE] => <snip>
    [HTTP_HOST] => <snip>
    [HTTP_KEEP_ALIVE] => 115
    [HTTP_USER_AGENT] => <snip>
    [PATH] => /bin:/usr/bin
    [QUERY_STRING] => 
    [REDIRECT_STATUS] => 200
    [REMOTE_ADDR] => <snip>
    [REMOTE_PORT] => 49262
    [REQUEST_METHOD] => GET
    [REQUEST_URI] => /~sitename/
**  [SCRIPT_FILENAME] => /home/sitename/public_html/index.php
    [SCRIPT_NAME] => /~sitename/index.php
    [SERVER_ADDR] => <snip>
    [SERVER_ADMIN] => <snip>
    [SERVER_NAME] => <snip>
    [SERVER_PORT] => 80
    [SERVER_PROTOCOL] => HTTP/1.1
    [SERVER_SIGNATURE] => 
Apache mod_fcgid/2.3.5 mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635 Server at <snip> Port 80


    [SERVER_SOFTWARE] => Apache mod_fcgid/2.3.5 mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635
    [UNIQUE_ID] => TVox-Eo1Z8IAAG1kAh4AAAEZ
    [PHP_SELF] => /~sitename/index.php
    [REQUEST_TIME] => 1297756668
    [argv] => Array
        (
        )

    [argc] => 0
)

And my machine:

Array
(
    [HTTP_AUTHORIZATION] => 
    [HTTP_HOST] => <snip>
    [HTTP_USER_AGENT] => <snip>
    [HTTP_ACCEPT] => text/html,application/xhtml+xml,application/xml;q=0.9;q=0.8
    [HTTP_ACCEPT_LANGUAGE] => en-gb,en;q=0.5
    [HTTP_ACCEPT_ENCODING] => gzip,deflate
    [HTTP_ACCEPT_CHARSET] => ISO-8859-1,utf-8;q=0.7,*;q=0.7
    [HTTP_KEEP_ALIVE] => 115
    [HTTP_CONNECTION] => keep-alive
    [PATH] => <snip>
    [SystemRoot] => C:\Windows
    [COMSPEC] => C:\Windows\system32\cmd.exe
    [PATHEXT] => .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
    [WINDIR] => C:\Windows
    [SERVER_SIGNATURE] => 
    [SERVER_SOFTWARE] => Apache/2.2.11 (Win32) PHP/5.3.1
    [SERVER_NAME] => <snip>
    [SERVER_ADDR] => <snip>
    [SERVER_PORT] => 80
    [REMOTE_ADDR] => <snip>
**  [DOCUMENT_ROOT] => C:/wamp/www/
    [SERVER_ADMIN] => admin@localhost
**  [SCRIPT_FILENAME] => C:/wamp/www/K2F/cms/cms-joomla-1.5/index.php
    [REMOTE_PORT] => 49947
    [GATEWAY_INTERFACE] => CGI/1.1
    [SERVER_PROTOCOL] => HTTP/1.1
    [REQUEST_METHOD] => GET
    [QUERY_STRING] => 
    [REQUEST_URI] => /K2F/cms/cms-joomla-1.5/
    [SCRIPT_NAME] => /K2F/cms/cms-joomla-1.5/index.php
    [PHP_SELF] => /K2F/cms/cms-joomla-1.5/index.php
    [REQUEST_TIME] => 1297758541
)

** Parts you ought to read out, should explain my problem perfectly.

So basically, the expected DOCUMENT_ROOT is /home/sitename/public_html/, but instead I got /usr/local/apache/htdocs.

Oh, and sorry if I've been a bit too verbose ;)

Edit:

getcwd() => /home/visitgoz/public_html

__FILE__ => /home/visitgoz/public_html/K2F/config.php

回答1:

Those (cheap) Mass-Hosters quite often do some Apache URL-Rewriting tricks - which basically make THEIR Life easier, since there's only ONE Apache V-Host, with ONE Document-Root for all shared Websites.

To find the "real" document Root in this case:

Compare DOCUMENT_ROOT to SCRIPT_FILENAME from left to right. If there are no matching Path-Components, it's such a shared host.
If it's such a shared host, remove REQUEST_URI from SCRIPT_NAME => "index.php" in your example.
Then: remove the result from above from the end of SCRIPT_FILENAME => your DOCUMENT_ROOT (/home/sitename/public_html/)

Edit (Christian Sciberras): This is the right answer, but it lacks code, which I had to write anyway, so here goes:

if(strpos($_SERVER['SCRIPT_FILENAME'],$_SERVER['DOCUMENT_ROOT'])===false){
    // how it works on reseller accounts...
    $path=str_common(getcwd(),__FILE__);
}else{
    // how it normally works...
    $path=truepath($_SERVER['DOCUMENT_ROOT']).'/';
}

回答2:

I would use dirname(__FILE__), dirname(dirname(__FILE__) . '/../..') or something like that to create constant DOCUMENT_ROOT which would then be used instead of $_SERVER['DOCUMENT_ROOT'].

回答3:

The document root is per virtual host. But using UserDir (e.g. ~sitename) tells the server to look elsewhere for the files to process. You will need to handle this difference if you want your script to work properly.