Description:
------------
The function "is_writable" does not work correctly:

The attached script does not give the correct result when run from the command line or from apache

the session.save_path is set to "/tmp" in php.ini which has the following permissions:

drwxrwxrwt   25 root     root         4096 Sep  2 23:30 tmp

this is the normal file permissions for the linux /tmp directory.

with these permissions any use can write into this directory, but the "is_writable" function returns "false"


Reproduce code:
---------------
<?php
   //checks if temp is writeable
   $sp=ini_get('session.save_path');
   echo $sp . "<br/>";
   if (is_writable($sp)) {      
      echo 'The file is writable';
   } else {
      echo 'The file is not writable';
   }
?>

Expected result:
----------------
/tmp<br/>The file is writable

Actual result:
--------------
/tmp<br/>The file is not writable