Benni Mack, CTO of b13 and TYPO3 Core Project Lead said:

“TYPO3 has been benefiting from PHP-FIG's standard recommendations for over 5 years, and participating as an active member in PHP-FIG was long overdue, in helping to shape the future of interoperability of PHP frameworks and Content Management Systems.”

The official announcement was posted by PHP-FIG 25 July 2020: