Dependent Plugin Activation/Deactivation and Alert

plugin.php

<?php
/*
 * Dependent Plugin Activation/Deactivation
 *
 * Sources:
 * 1. https://pippinsplugins.com/checking-dependent-plugin-active/
 * 2. http://10up.com/blog/2012/wordpress-plug-in-self-deactivation/
 *
 */

function child_plugin_init() {

    // If Parent Plugin is NOT active
    if ( current_user_can( 'activate_plugins' ) && !class_exists( 'Parent Plugin Class' ) ) {

        add_action( 'admin_init', 'my_plugin_deactivate' );
        add_action( 'admin_notices', 'my_plugin_admin_notice' );

        // Deactivate the Child Plugin
        function my_plugin_deactivate() {
          deactivate_plugins( plugin_basename( __FILE__ ) );
        }

        // Throw an Alert to tell the Admin why it didn't activate
        function my_plugin_admin_notice() {
            $dpa_child_plugin = __( 'Child Plugin', 'textdomain' );
            $dpa_parent_plugin = __( 'Parent Plugin', 'textdomain' );

            echo '<div class="error"><p>'
                . sprintf( __( '%1$s requires %2$s to function correctly. Please activate %2$s before activating %1$s. For now, the plugin has been deactivated.', 'textdomain' ), '<strong>' . esc_html( $dpa_child_plugin ) . '</strong>', '<strong>' . esc_html( $dpa_parent_plugin ) . '</strong>' )
                . '</p></div>';

           if ( isset( $_GET['activate'] ) )
                unset( $_GET['activate'] );
        }

    } else {

        // include all your plugin files here

    }
}

add_action( 'plugins_loaded', 'child_plugin_init' );