copy_dir()

function copy_dir( $from, $to, $skip_list = array() ) {
	global $gc_filesystem;

	$dirlist = $gc_filesystem->dirlist( $from );

	if ( false === $dirlist ) {
		return new GC_Error( 'dirlist_failed_copy_dir', __( 'Directory listing failed.' ), basename( $to ) );
	}

	$from = trailingslashit( $from );
	$to   = trailingslashit( $to );

	foreach ( (array) $dirlist as $filename => $fileinfo ) {
		if ( in_array( $filename, $skip_list, true ) ) {
			continue;
		}

		if ( 'f' === $fileinfo['type'] ) {
			if ( ! $gc_filesystem->copy( $from . $filename, $to . $filename, true, FS_CHMOD_FILE ) ) {
				// If copy failed, chmod file to 0644 and try again.
				$gc_filesystem->chmod( $to . $filename, FS_CHMOD_FILE );

				if ( ! $gc_filesystem->copy( $from . $filename, $to . $filename, true, FS_CHMOD_FILE ) ) {
					return new GC_Error( 'copy_failed_copy_dir', __( 'Could not copy file.' ), $to . $filename );
				}
			}

			gc_opcache_invalidate( $to . $filename );
		} elseif ( 'd' === $fileinfo['type'] ) {
			if ( ! $gc_filesystem->is_dir( $to . $filename ) ) {
				if ( ! $gc_filesystem->mkdir( $to . $filename, FS_CHMOD_DIR ) ) {
					return new GC_Error( 'mkdir_failed_copy_dir', __( 'Could not create directory.' ), $to . $filename );
				}
			}

			// Generate the $sub_skip_list for the subdirectory as a sub-set of the existing $skip_list.
			$sub_skip_list = array();

			foreach ( $skip_list as $skip_item ) {
				if ( 0 === strpos( $skip_item, $filename . '/' ) ) {
					$sub_skip_list[] = preg_replace( '!^' . preg_quote( $filename, '!' ) . '/!i', '', $skip_item );
				}
			}

			$result = copy_dir( $from . $filename, $to . $filename, $sub_skip_list );

			if ( is_gc_error( $result ) ) {
				return $result;
			}
		}
	}

	return true;
}

// Connecting to the filesystem.
if ( ! GC_Filesystem() ) {
	// Unable to connect to the filesystem, FTP credentials may be required or something.
	// You can request these with request_filesystem_credentials()
	exit;
}

// Don't forget that the target directory needs to exist.
// If it doesn't already, you'll need to create it.
global $gc_filesystem;
$gc_filesystem->mkdir( $target_dir );

// Now copy all the files in the source directory to the target directory.
copy_dir( $src_dir, $target_dir );