Description:
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There are legitimate "secure-operation" situations when you want the include path wiped out, so that all included files must be explicitly stated.

The obvious way to set this is with either:
set_include_path(''); // or
ini_set('include_path', '');

However, neither one of these sets the include path to '' on the latest version of PHP 4 or PHP 5 in Linux.

A non-obvious workaround is to use a whitespace string:
set_include_path(' '); // or
ini_set('include_path', ' ');

which does set the path to ' ' (which hopefully isn't a valid directory!).

I believe passing a lambda string to either set_include_path or ini_set('include_path') should set the path to the lambda string.

http://bytejar.com/ - Software Lessons Learned the Hard Way

Reproduce code:
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$original_path = set_include_path('');


Expected result:
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'' === get_include_path();

Actual result:
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$original_path === get_include_path();