The iOS lib emojione.m file contains the function _loadShortNameToUnicode
which maps shorthand codes to unicode characters.
The php lib src ruleset.php shortcode_replace function contains more shortcode to unicode conversions.

Basically the two dictionaries do not represent the same emoji shorthands, so using them respectively for web and iOS produces inconsistencies in parsing the same unicode between the two platforms.

Please update the iOS dictionary to reflect what's in the PHP dictionary.
Also note the Emoji 11.0 spec is being implemented by Apple in September.
https://blog.emojipedia.org/whats-new-in-unicode-11-0/