Parameters 
  - $path
-   (string) (Required) Path for new directory.  
- $chmod
-   (int|false) (Optional)  The permissions as octal number (or false to skip chmod).   Default value: false 
- $chown
-   (string|int) (Optional)  A user name or number (or false to skip chown).   Default value: false 
- $chgrp
-   (string|int) (Optional)  A group name or number (or false to skip chgrp).   Default value: false 
Return 
 (bool) True on success, false on failure.
    Source 
  File: wp-admin/includes/class-wp-filesystem-ftpext.php 
 public function mkdir( $path, $chmod = false, $chown = false, $chgrp = false ) {
		$path = untrailingslashit( $path );
		if ( empty( $path ) ) {
			return false;
		}
		if ( ! ftp_mkdir( $this->link, $path ) ) {
			return false;
		}
		$this->chmod( $path, $chmod );
		return true;
	}       Changelog 
     | Version | Description | 
    | 2.5.0 | Introduced. |