(PECL xattr >= 0.9.0)
xattr_set — Set an extended attribute
$filename
   , string $name
   , string $value
   [, int $flags = 0
  ] )This function sets the value of an extended attribute of a file.
Extended attributes have two different namespaces: user
and root. The user namespace is available to all users, while the root namespace
is available only to users with root privileges. xattr operates on the user
namespace  by default, but this can be changed with the
flags parameter.
filenameThe file in which we set the attribute.
name
       The name of the extended attribute. This attribute will be created if 
       it doesn't exist or replaced otherwise. You can change this behaviour 
       by using the flags parameter.
      
valueThe value of the attribute.
flags
| XATTR_CREATE | Function will fail if extended attribute already exists. | 
| XATTR_REPLACE | Function will fail if extended attribute doesn't exist. | 
| XATTR_DONTFOLLOW | Do not follow the symbolic link but operate on symbolic link itself. | 
| XATTR_ROOT | Set attribute in root (trusted) namespace. Requires root privileges. | 
   Returns TRUE on success or FALSE on failure.
  
Example #1 Sets extended attributes on .wav file
<?php
$file = 'my_favourite_song.wav';
xattr_set($file, 'Artist', 'Someone');
xattr_set($file, 'My ranking', 'Good');
xattr_set($file, 'Listen count', '34');
/* ... other code ... */
printf("You've played this song %d times", xattr_get($file, 'Listen count')); 
?>