php - PHPass producing warning: is_readable() [function.is-readable]: open_basedir restriction in effect

I'm using PHPass to encrypt passwords stored in my database. When running this code:

if (is_readable('/dev/urandom') && ($fh = @fopen('/dev/urandom', 'rb'))) {
    ...
}

it produces this warning:

Warning: is_readable() [function.is-readable]: open_basedir restriction in effect. File(/dev/urandom) is not within the allowed path(s):
(/home/d36234:/usr/local/lib/php:/var/apachefs/uploads:/tmp:/etc/file/magic) in /home/d36234/.../PasswordHash.php on line 51

What's wrong here, and how do I fix it?