Admin email sender plugin

admin-email-sender.php

<?php
/**
 * Plugin Name: Admin Email Sender
 * Description: Adds a wp-admin page that lets administrators send plain-text emails using WordPress wp_mail().
 * Version: 1.0.0
 * Author: Your Name
 * License: GPL-2.0-or-later
 */

if (!defined('ABSPATH')) {
    exit;
}

class Admin_Email_Sender {
    const MENU_SLUG = 'admin-email-sender';
    const NONCE_ACTION = 'admin_email_sender_send';
    const NONCE_NAME = 'admin_email_sender_nonce';

    public function __construct() {
        add_action('admin_menu', [$this, 'add_admin_page']);
        add_action('admin_post_admin_email_sender_send', [$this, 'handle_send']);
    }

    public function add_admin_page() {
        add_menu_page(
            __('Email Sender', 'admin-email-sender'),
            __('Email Sender', 'admin-email-sender'),
            'manage_options',
            self::MENU_SLUG,
            [$this, 'render_page'],
            'dashicons-email-alt',
            80
        );
    }

    public function render_page() {
        if (!current_user_can('manage_options')) {
            wp_die(esc_html__('You do not have permission to access this page.', 'admin-email-sender'));
        }

        $status = isset($_GET['aes_status']) ? sanitize_key($_GET['aes_status']) : '';
        ?>
        <div class="wrap">
            <h1><?php echo esc_html__('Email Sender', 'admin-email-sender'); ?></h1>

            <?php if ($status === 'sent') : ?>
                <div class="notice notice-success is-dismissible">
                    <p><?php echo esc_html__('Email sent successfully.', 'admin-email-sender'); ?></p>
                </div>
            <?php elseif ($status === 'failed') : ?>
                <div class="notice notice-error is-dismissible">
                    <p><?php echo esc_html__('Email could not be sent. Check your WordPress mail configuration.', 'admin-email-sender'); ?></p>
                </div>
            <?php elseif ($status === 'invalid') : ?>
                <div class="notice notice-error is-dismissible">
                    <p><?php echo esc_html__('Please enter a valid recipient email address, subject, and message.', 'admin-email-sender'); ?></p>
                </div>
            <?php endif; ?>

            <form method="post" action="<?php echo esc_url(admin_url('admin-post.php')); ?>">
                <?php wp_nonce_field(self::NONCE_ACTION, self::NONCE_NAME); ?>
                <input type="hidden" name="action" value="admin_email_sender_send">

                <table class="form-table" role="presentation">
                    <tr>
                        <th scope="row">
                            <label for="aes_to"><?php echo esc_html__('To', 'admin-email-sender'); ?></label>
                        </th>
                        <td>
                            <input name="aes_to" id="aes_to" type="email" class="regular-text" required>
                        </td>
                    </tr>

                    <tr>
                        <th scope="row">
                            <label for="aes_subject"><?php echo esc_html__('Subject', 'admin-email-sender'); ?></label>
                        </th>
                        <td>
                            <input name="aes_subject" id="aes_subject" type="text" class="regular-text" required>
                        </td>
                    </tr>

                    <tr>
                        <th scope="row">
                            <label for="aes_message"><?php echo esc_html__('Message', 'admin-email-sender'); ?></label>
                        </th>
                        <td>
                            <textarea name="aes_message" id="aes_message" rows="10" class="large-text" required></textarea>
                        </td>
                    </tr>
                </table>

                <?php submit_button(__('Send Email', 'admin-email-sender')); ?>
            </form>
        </div>
        <?php
    }

    public function handle_send() {
        if (!current_user_can('manage_options')) {
            wp_die(esc_html__('You do not have permission to send emails.', 'admin-email-sender'));
        }

        check_admin_referer(self::NONCE_ACTION, self::NONCE_NAME);

        $to = isset($_POST['aes_to']) ? sanitize_email(wp_unslash($_POST['aes_to'])) : '';
        $subject = isset($_POST['aes_subject']) ? sanitize_text_field(wp_unslash($_POST['aes_subject'])) : '';
        $message = isset($_POST['aes_message']) ? sanitize_textarea_field(wp_unslash($_POST['aes_message'])) : '';

        if (!is_email($to) || empty($subject) || empty($message)) {
            $this->redirect_with_status('invalid');
        }

        $headers = ['Content-Type: text/plain; charset=UTF-8'];
        $sent = wp_mail($to, $subject, $message, $headers);

        $this->redirect_with_status($sent ? 'sent' : 'failed');
    }

    private function redirect_with_status($status) {
        wp_safe_redirect(
            add_query_arg(
                'aes_status',
                sanitize_key($status),
                admin_url('admin.php?page=' . self::MENU_SLUG)
            )
        );
        exit;
    }
}

new Admin_Email_Sender();