What the hell with WHMCS support!.
Originally, json is embed to php. But you can non-embed with '--disable-json'. Because json including in php src, 'disable' mean json still installed if you installing php but as module. In another word, 'including in src' but 'disable' mean '--with-json'.
You can see inside '/etc/php.d', file json.ini exist on not.
To proof, json active or not you can see with phpinfo() or run 'php -m' via ssh.
That it.
So... What the hell with WHMCS support!.