The xattr extension allows for the manipulation of extended attributes on a filesystem.
To use xattr, you will need libattr installed. It is available at » http://oss.sgi.com/projects/xfs/.
These functions only work on filesystems that support extended attributes, and have them enabled at mount time. Some common filesystems that support extended attributes are ext2, ext3, reiserfs, jfs, and xfs.
xattr is currently available through PECL » http://pecl.php.net/package/xattr.
If » PEAR is available on your *nix-like system you can use the pear installer to install the xattr extension, by the following command: pear -v install xattr.
You can always download the tar.gz package and install xattr by hand:
tar -xvf xattr-xxx.tar
./configure && make && make install
The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.