plugin development - Share functions between admin and frontend

I'm new to OOPs. I'm building a Plugin and I started with the "Wordpress Plugin Boilerplate with Namespace and AutoLoader Support."

I've even successfully added a section for a RESTful interface that I got working. However I have a a few functions that are common between Admin, the Front end and my REST interface. It would seem reasonable to put those common functions in the /inc/common folder. But I can not get it working.

Perhaps it is clear to a more experienced OOPs programmer, but I have found no guidance on the web. How should these functions/menthods? be packaged in /inc/common and how should they be called?

Plugin has folders:

    /inc/admin -contains class admin
    /inc/frontend -contains class frontend
    /inc/libraries -contains class autoloader
    /inc/core - contains class activator/deactivator/int/loader 
    /inc/common - empty folder
    /inc/rest (I added) 

I have tried just putting functions in a file in /int/common/common.php :

    function common(){
       do something
     }

the including them from class admin/frontend/rest - that does not work. I have tried wrapping the functions in a class common:

    class common{
       public function common(){
        do something
       }
      } 

no luck there. I've gotten it so hosed up I had to restore from a working back up to got back to where I was last week so I load my code attempt. Some clue as to how to approach this is what I am looking for because clearly I'm missing something major here.

As best as I can recreate what I had:

Function in /inc/rest/class-rest

    namespace PGC_Signoffs\Inc\Rest;
    class Rest {
        public function glider_club_update_signoff( \WP_REST_Request  $request) {
         include_once plugin_dir_path( __DIR__ ) . 'common/common.php';

         $date_expire = $common_function($a,$b,$c); 
         }
    }   

Function in inc/common/common.php

    public common_function( $a, $b, c){
        // function to calculate the expire date. 
       return($start_date); 
    }

I'm new to OOPs. I'm building a Plugin and I started with the "Wordpress Plugin Boilerplate with Namespace and AutoLoader Support."

I've even successfully added a section for a RESTful interface that I got working. However I have a a few functions that are common between Admin, the Front end and my REST interface. It would seem reasonable to put those common functions in the /inc/common folder. But I can not get it working.

Perhaps it is clear to a more experienced OOPs programmer, but I have found no guidance on the web. How should these functions/menthods? be packaged in /inc/common and how should they be called?

Plugin has folders:

    /inc/admin -contains class admin
    /inc/frontend -contains class frontend
    /inc/libraries -contains class autoloader
    /inc/core - contains class activator/deactivator/int/loader 
    /inc/common - empty folder
    /inc/rest (I added) 

I have tried just putting functions in a file in /int/common/common.php :

    function common(){
       do something
     }

the including them from class admin/frontend/rest - that does not work. I have tried wrapping the functions in a class common:

    class common{
       public function common(){
        do something
       }
      } 

no luck there. I've gotten it so hosed up I had to restore from a working back up to got back to where I was last week so I load my code attempt. Some clue as to how to approach this is what I am looking for because clearly I'm missing something major here.

As best as I can recreate what I had:

Function in /inc/rest/class-rest

    namespace PGC_Signoffs\Inc\Rest;
    class Rest {
        public function glider_club_update_signoff( \WP_REST_Request  $request) {
         include_once plugin_dir_path( __DIR__ ) . 'common/common.php';

         $date_expire = $common_function($a,$b,$c); 
         }
    }   

Function in inc/common/common.php

    public common_function( $a, $b, c){
        // function to calculate the expire date. 
       return($start_date); 
    }

• plugin-development

Share Improve this question edited Feb 12, 2019 at 22:39 dsj asked Feb 12, 2019 at 21:10 dsjdsj 6388 bronze badges 5

• I used a similar (if not the same, I can't remember) boilerplate a few months ago, and as far as I can tell being functions shared between a restricted area (admin) and a public one (REST, frontend) you should treat them as frontend functions, and hook them to admin hooks in the Init() class. But please tell us more: provide a minimal code example, explain us how you tried and cannot make it work, explain to us the project skeleton, etc. – Fabrizio Mele Commented Feb 12, 2019 at 21:40
• There's no code in your question, how are the classes inside inc/common being loaded at the moment? Are you loading them? Or do you expect that if you create a class in that folder it will just load auto-magically? Where do you create those objects? – Tom J Nowell ♦ Commented Feb 12, 2019 at 22:01
• (this is the boilerplate he's talking about) – Fabrizio Mele Commented Feb 12, 2019 at 22:02
• I'm not trying to hook directly to these functions. These are common functions used by functions that are hooked in both admin/frontend and REST. – dsj Commented Feb 12, 2019 at 22:22
• a couple of notes: $common_function($a,$b,$c) is wrong, there is a $ too much before the function name. While this could work, I suggest you wrap that common_function inside a class and autoload it, look at my answer below – Fabrizio Mele Commented Feb 12, 2019 at 22:41

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1 Answer 1

Sorted by: Reset to default 0

That boilerplate uses autoloading, take advantage of it! I understand it's a bit overwhelming but with some training you will realize that autoloading and OOP are a superlative productivity boost.

Inside inc/common create your class (for example, class-commonclass.php)

<?php

namespace PGC_Signoffs\Inc\Common; \\declare the namespace for autoloading

class CommonClass {

  public function commonFunction($a,$b,$c){ //could also be 'public static function'
    //do your magic
    return $start_date;
  }

}

Note: the functions inside CommonClass could be static, it depends on what you want to do with the class. If it's just a collection of functions go with static.

Then instance the class inside other classes, for example Admin:

<?php
namespace PGC_Signoffs\Inc\Rest;

use PGC_Signoffs\Inc\Common\CommonClass; //declare you will be using CommonClass from the Inc\Common namespace

class Rest{
  ...

  public function glider_club_update_signoff( \WP_REST_Request  $request) {

    $commonClass = new CommonClass();
    $date_expire = $commonClass->commonFunction($a,$b,$c);
    //or, if you went with a static function:
    $date_expire = CommonClass::commonFunction($a,$b,$c);
  }
}

Here's the gist