Change Details

- expand documentation about PHP Pitfalls to mention strlen() deprecation - mention is_string() - mention phutil_nonempty_string() - link from PHP Contributors Manual Ref T15190

- expand documentation about PHP Pitfalls to mention strlen() in PHP 8.1 - mention phutil_string_cast() - mention phutil_nonempty_string() - add a commodity link from PHP Contributors Manual Ref T15190

- expand documentation about PHP Pitfalls to mention strlen() deprecationin PHP 8.1 - mention isphutil_string_cast() - mention phutil_nonempty_string() - add a commodity link from PHP Contributors Manual Ref T15190