PHP 7.3.1 Lands A Bunch Of Fixes For This Fastest PHP Release Yet
PHP 7.3 adds WebP support to the GD imagecreatefromstring(), updated SQLite, an is_countable() function, and other convenient improvements but arguably most notable is PHP 7.3 still improving the PHP performance compared to prior PHP7 releases. So even ignoring the language additions, PHP 7.3 is worthwhile for web hosts simply due to the noticeable performance improvements.
With today's PHP 7.3.1 release there are many bug fixes as outlined at PHP.net. With PHP 7.0 now being end-of-life, it's a good time to upgrade.