Description:
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I'm testing the new feature introduced lately, namely "tightening" the open_basedir setting. This might be a very good security measure, to prevent relative directory traversal exploits.

However, sometimes it is useful to tighten the path only for certain code, and untighten it again afterward to its original value. This doesn't seem to work currently.

Reproduce code:
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<?php

// original open_basedir value
echo ini_get( 'open_basedir' ) . PHP_EOL;

$newBaseDir = dirname( __FILE__ ) . DIRECTORY_SEPARATOR . 'var' . DIRECTORY_SEPARATOR;

ini_set( 'open_basedir', $newBaseDir );

// new tightened open_basedir value
echo ini_get( 'open_basedir' ) . PHP_EOL;

// this will fail, as intended, because of the open_basedir restriction
file_put_contents( dirname( __FILE__ ) . DIRECTORY_SEPARATOR . 'test.txt', 'test 123 456' );

ini_restore( 'open_basedir' );

// original open_basedir value again
echo ini_get( 'open_basedir' ) . PHP_EOL;

// this will stail fail, not intended
file_put_contents( dirname( __FILE__ ) . DIRECTORY_SEPARATOR . 'test.txt', 'test 123 456' );

?>

Expected result:
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The last call should be allowed, and a file test.txt should have been created in the same directory as the script.

Actual result:
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Warning: file_put_contents(): open_basedir restriction in effect. File(C:\sites\
trunk\test.txt) is not within the allowed path(s): (&#9617;&#948;?&#9786;&#9792;) in ...

Warning: file_put_contents(C:\sites\trunk\test.txt): failed to open stream: Operation not permitted in ...