How do I get the number of rows affected from an update query?
$update_query-&gt;execute()-&gt;rowCount() would cause a Call to a member function rowCount() on a non-object (or Call to a member function rowCount() on int, on PHP 7.4) since $update_query-&gt;execute() returns the number of rows  matched by the update query, including the ones that actually didn't have to be updated.
rowCount() can be called only when execute() returns an object implementing StatementInterface, which is the case for Select::execute(), Truncate::execute(), Upsert::execute(), and Query::execute().
Unfortunately, the only way to get the number of rows changed from an update query is to fetch the rows matching the update condition (in your case, the rows for which uid is equal to $uid), and count which rows have, for the desired fields (in your case, name_of_user, url, website, industry, company_size, company_type, headquarters, founded, page_picture, tagline, and updated_at), a value different from the value set by the update query.