Function: Creates a file in the upload folder with given content.

Function: Retrieves the file type based on the extension name.

Function: Recursive directory creation based on full path.

Function: Tests if a given filesystem path is absolute.

Function: Joins two filesystem paths together.

Function: Retrieves URL with nonce added to URL query.

Function: Retrieves or display nonce hidden field for forms.

Function: Retrieves or displays referer hidden field for forms.

Function: Retrieves or displays original referer hidden field for forms.

Function: Retrieves referer from ‘_wp_http_referer’ or HTTP referer.