Example helper module that adds a new system variable "$helper" with a method to generate FontAwesome markup for use in templates

MyHelper.module

<?php

class MyHelper extends WireData implements Module {
    /**
     * getModuleInfo is a method required by all modules to tell ProcessWire about them
     * @return array
     */
    public static function getModuleInfo() {
        return array(
            'title' => 'My Helper Module',
            'version'=> 1,
            'summary' => 'Example Helper Module to generate FontAwesome icon markup.',
            'author' => 'me',
            'singular' => true,
            'autoload' => true
            );
    }

    public function init(){
        $this->set("icon_prefix", "fa");
        wire("fuel")->set("helper", $this);
    }

    public function faIcon($name, $size = ''){
        if($size){
            $size = " {$this->icon_prefix}-$size";
        }
        return "<i class='{$this->icon_prefix} {$this->icon_prefix}-$name{$size}'></i>";
    }
    
}