php set_include_path drives me crazy

I need to include a file in php so I do

$web_proc = '../res/proc'; //variable read from config file I can't change
//in my file
include_once($web_proc . '/check_sprache.php');

and PHP outputs:

Warning: include_once(../res/proc/check_sprache.php): failed to open stream: No such file or directory in /Users/user/Sites/site/res/pdf/rechnung.php on line 62
Warning: include_once(): Failed opening '../res/proc/check_sprache.php' for inclusion (include_path='.:') in /Users/user/Sites/site/res/pdf/rechnung.php on line 62

So I change the include path:

set_include_path(get_include_path() . PATH_SEPARATOR . dirname(__DIR__) . DIRECTORY_SEPARATOR);

and try it again, but PHP outputs:

Warning: include_once(../res/proc/check_sprache.php): failed to open stream: No such file or directory in /Users/user/Sites/site/res/pdf/rechnung.php on line 62
Warning: include_once(): Failed opening '../res/proc/check_sprache.php' for inclusion (include_path='.::/Users/user/Sites/site/res/') in /Users/user/Sites/site/res/pdf/rechnung.php on line 62

But if if I do

include_once(dirname(__DIR__). DIRECTORY_SEPARATOR . $pfadweb_proc . '/check_sprache.php');

it works. But this is no solution, since the included file includes more files with a relative path, so they are alse not found.

So either I misunderstand the PHP include path, or it's just trolling me.

Can anybody help?

Solution

The include path looks odd in the second example; You have two PATH_SEPARATOR characters and a trailing DIRECTORY_SEPARATOR though I doubt this is the problem.

Try this one out instead

set_include_path(implode(PATH_SEPARATOR, [ // use array() if PHP < 5.4
    dirname(__DIR__), // this should be /Users/user/Sites/site/res
    get_include_path()
]));

include_once 'proc/check_sprache.php';

This will add the parent directory (/Users/user/Sites/site/res) of the CWD (/Users/user/Sites/site/res/pdf) to your include path.

Any include statements in any other files can use a relative path from /Users/user/Sites/site/res.