An update: I had to go back to 4.3.8. I kept getting the following error (among others) from init.php whenever I tried to use the PungoSpell spell checker.
It said function.implode was not an array in this query:
PHP Code:
$datastoretemp = $DB_site->query("
SELECT title, data FROM " . TABLE_PREFIX . "datastore
WHERE title IN ('" . implode("', '", $specialtemplates) . "')
");
unset($specials, $specialtemplates);
It nailed function.merge (array_merge) in here too and another one in global.php.
So, apparently, there are areas it needs work on, I guess.