无法打开流：没有这样的文件或目录，是的！

root/
    test.php
    test/
        test2.php
        sub/
            test3.php

echo    \'test\';
require \'test/sub/test3.php\';

echo    \'test2\';

echo    \'test3\';
/* 
because we are still on test.php, the include path is the root
that means the following would work:
require \'test/test2.php\';
however I don\'t know this path in this file. (it\'s dynamic)
I thought this would work:
*/
set_include_path(dirname(__FILE__));
require \'../test2.php\';

set_include_path(dirname(__FILE__));
require \'../test2.php\';

set_include_path(dirname(__FILE__).\"/../\"));
require \'test2.php\';

testtest3
Warning: require(../test2.php) [function.require]: failed to open stream: No such file or directory in siteroot/test/sub/test3.php on line 6

Fatal error: require() [function.require]: Failed opening required \'../test2.php\' (include_path=\'siteroot/test/sub\') in siteroot/test/sub/test3.php on line 6

test3.php

echo \'<pre>\';
print_r(scandir(dirname(__FILE__).\'/../\'));
echo \'</pre>\';

Array
(
    [0] => .
    [1] => ..
    [2] => sub
    [3] => test2.php
)