PHP is capable of receiving file uploads from any RFC-1867 compliant browser.
Local means that it’s persistent, and session is simply that the data is lost when the session ends (i.e. It’s also worth noting that a session is tied to a single browser window or tab.
While HTML, prior to HTML5, was defined as an application of Standard Generalized Markup Language (SGML), a flexible markup language framework, XHTML is an application of XML, a more restrictive subset of SGML.
XHTML documents are well-formed and may therefore be parsed using standard XML parsers, unlike HTML, which requires a lenient HTML-specific parser.
This form element should always be used as it saves users the trouble of waiting for a big file being transferred only to find that it was too large and the transfer failed.
Keep in mind: fooling this setting on the browser side is quite easy, so never rely on files with a greater size being blocked by this feature.