Description:
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if used filename as folder in your path the file system function(is_dir,is_file,file_exists and etc ...) shows a restriction warning.

i thinks , this is a bug.

Test script:
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run this codes :

root#
mkdir /test
touch /test/empty
echo "<?php var_dump(is_file('/test/empty/foo/bar'));" > /test/index.php
echo "open_basedir = /test" > /test/php.ini


then :
root# php -c /test/php.ini /test/index.php

Warning: is_file(): open_basedir restriction in effect. File(/test/empty/foo/bar) is not within the allowed path(s): (/test) in /test/index.php on line 1
bool(false)

Expected result:
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no a restriction warning.

Actual result:
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shows a restriction warning.