Custom Article plugin loses functionality after article creation

Question

I have created a plugin that adds a radio selection and text fields to back-end Article creation (and I thought edit as well) but the functionality behind those custom inputs only fires on creation. I need the functionality to apply on edit saves as well since the article in question will be used dozens of times. Is there a way to make this happen?

plugin XML:

<?xml version="1.0" encoding="utf-8"?>
<extension version="3.4" type="plugin" group="content" method="upgrade">
    <name>plg_content_articlepublishemail</name>
    <author>---</author>
    <creationDate>July 2016</creationDate>
    <copyright>(C) 2005 - 2016 Open Source Matters. All rights reserved.</copyright>
    <license>GNU General Public License version 2 or later; see LICENSE.txt</license>
    <authorEmail>---</authorEmail>
    <authorUrl>---</authorUrl>
    <version>1.0</version>
    <description>PLG_CONTENT_ARTICLEPUBLISHEMAIL_XML_DESCRIPTION</description>
    <files>
        <folder>language</folder>
        <folder>forms</folder>
        <filename plugin="articlepublishemail">articlepublishemail.php</filename>
    </files>
    <languages>
        <language tag="en-GB">en-GB.plg_content_articlepublishemail.ini</language>
    </languages>      
    <config>
        <fields name="params">
        </fields>
    </config>
</extension>

content XML:

<?xml version="1.0" encoding="utf-8"?>
<form>
    <fields name="attribs">
        <fieldset name="articlepublishemail" label="Emailer">
            <field
                name="email_send"
                type="radio"
                default="0"
                label="PLG_CONTENT_ARTICLEPUBLISHEMAIL_EMAIL_SEND_LABEL">
                <option name="sendoff" id="sendoff" value="0">JOFF</option>
                <option name="sendon" id="sendon" value="1">JON</option>
            </field>
            <field
                name="first_email_sendto"
                type="text"
                label="PLG_CONTENT_ARTICLEPUBLISHEMAIL_FIRST_EMAIL_SENDTO_LABEL"
            />
            <field
                name="second_email_sendto"
                type="text"
                label="PLG_CONTENT_ARTICLEPUBLISHEMAIL_SECOND_EMAIL_SENDTO_LABEL"
            />
            <field
                name="third_email_sendto"
                type="text"
                label="PLG_CONTENT_ARTICLEPUBLISHEMAIL_THIRD_EMAIL_SENDTO_LABEL"
            />
        </fieldset>
    </fields>
</form>

PHP:

<?php
defined( '_JEXEC' ) or die;

class plgContentArticlepublishemail extends JPlugin
{
    protected $autoloadLanguage = true;

    function onContentPrepareForm($form,$data)
    {
        if(!($form instanceof JForm))
        {
            $this->_subject->setError('JERROR_NOT_A_FORM');
            return false;
        }

        $option = $app->input->get('option');

        switch($option)
        {
            case 'com_content' :
                if ($app->isAdmin())
                {
                    JForm::addFormPath(__DIR__ . '/forms');
                    $form->loadFile('content',false);
                }
                return true;
        }
        return true;
    }

    function onContentBeforeSave($context, $article, $isNew)
    {
        $id = $article->id ;

        $app = JFactory::getApplication();

        $attribs = json_decode($article->attribs);

        $confirmed_to_send = "" . $attribs->email_send ;

        if($confirmed_to_send == '1')
        {
            // do some stuff with the sendto fields
        }
        return true;
    }
}
?>

Answer 1

Through waarnemer's suggestion on the Joomla forums, simply by switching the plugin event from onContentBeforeSave to onContentAfterSave, functionality remained after initial save. This seems to have been a blunder on my part in that I did not understand exactly what the Plugin/Events/Content tutorial was trying to convey for those two events.