The PHP ftp_cdup() function changes to the parent directory on the FTP server.

<?php
// connect and login to FTP server
$ftp_server = 'ftp.example.com';

$ftp_conn = ftp_connect($ftp_server) or die('Could not connect to ' . $ftp_server);
$login = ftp_login($ftp_conn, $ftp_username, $ftp_userpass);

$file = '/test/my-file';

// change the current directory to php
ftp_chdir($ftp_conn, 'php');

// change to the parent directory
if (ftp_cdup($ftp_conn)) {
    echo 'Changed to the parent directory.';
}
else {
    echo 'cdup failed.';
}

// output current directory name
echo ftp_pwd($ftp_conn);

// close connection
ftp_close($ftp_conn);
?>

// outputs the current directory name, then changes to the parent directory

ftp_cdup(ftp_conn)