\lstset{
    language=PHP,
    alsoletter={\$},
    basicstyle=\ttfamily,
    numbers=left,
    frame=single,
    breaklines=true,
    breakatwhitespace=true,
    columns=flexible,
    keywordstyle=\color{blue},
    keywordstyle=[2]\color{teal}, % Var & Useful functions.
    keywordstyle=[3]\color{purple},
    commentstyle=\color{lightgray}\itshape,
    stringstyle=\color{orange},
    numberstyle=\color{lightgray},
    showstringspaces=false,
    morekeywords={
        require_once,
        public,
        protected,
        private,
        final,
        static,
        function,
        return,
        function,
        namespace,
        global,
        defined,
        class,
        abstract,
        interface,
        new,
        string,
        int,
    }, % PHP Keywords.
    morekeywords=[2]{
        \$_romhackplaza,
        \$_romhackplaza_theme,
        \$post_id,
        \$this,
        \$post_types,
        \$context,
    }, % Plugin useful vars.
    morekeywords=[3]{
        do_action,
        add_action,
        add_filter,
        apply_filters,
        CPT
    } % Plugin & WP useful functions.
}