chown

<?

$filename = $_SERVER['DOCUMENT_ROOT'] . '/assets/txt/1.txt';
$user = "root";

$return = chown($filename, $user);

var_export($return);

?>

true

<?

$filename = $_SERVER['DOCUMENT_ROOT'] . '/assets/txt/1.txt';
$user = "root";

chown($filename, $user);

$stat = stat($filename);
$uid = $stat['uid'];
$posix_getpwuid = posix_getpwuid($uid);

print_r($posix_getpwuid);

?>

Array
(
    [name] => root
    [passwd] => x
    [uid] => 0
    [gid] => 0
    [gecos] => root
    [dir] => /root
    [shell] => /bin/bash
)