Simple WordPress contact form that sends an admin email when submissions happen.

basic-contact-form.php

<?php
/*
Plugin Name: Basic Contact Form
Plugin URI: https://kevinleary.net
Description: A simple contact form plugin that sends email submissions using wp_mail().
Version: 1.0
Author: kevinlearynet
Author URI: https://kevinleary.net
*/

// Register the shortcode for the contact form
function basic_contact_form_shortcode()
{
    ob_start();

    if (
        $_SERVER["REQUEST_METHOD"] == "POST" &&
        isset($_POST["basic_contact_form_submit"])
    ) {
        $name = sanitize_text_field($_POST["name"]);
        $email = sanitize_email($_POST["email"]);
        $inquiry_type = sanitize_text_field($_POST["inquiry_type"]);
        $message = sanitize_textarea_field($_POST["message"]);
        $admin_email = get_option("admin_email");

        if (
            !empty($name) &&
            !empty($email) &&
            is_email($email) &&
            !empty($message)
        ) {
            $subject = "New Inquiry: $inquiry_type";
            $body = "Name: $name\nEmail: $email\nInquiry Type: $inquiry_type\n\nMessage:\n$message";
            $headers = ["Content-Type: text/plain; charset=UTF-8"];

            if (wp_mail($admin_email, $subject, $body, $headers)) {
                echo "<p>Thank you for your submission. We will get back to you shortly.</p>";
            } else {
                echo "<p>There was an issue sending your message. Please try again later.</p>";
            }
        } else {
            echo "<p>Please fill in all fields correctly.</p>";
        }
    }
    ?>
    <form method="post">
        <p>
            <label for="name">Name</label>
            <input type="text" id="name" name="name" required>
        </p>
        <p>
            <label for="email">Email</label>
            <input type="email" id="email" name="email" required>
        </p>
        <p>
            <label for="inquiry_type">Inquiry Type</label>
            <select id="inquiry_type" name="inquiry_type" required>
                <option value="Donate">Donate</option>
                <option value="Questions">Questions</option>
                <option value="Feedback">Feedback</option>
                <option value="Other">Other</option>
            </select>
        </p>
        <p>
            <label for="message">Message</label>
            <textarea id="message" name="message" rows="5" required></textarea>
        </p>
        <p>
            <button type="submit" name="basic_contact_form_submit">Send</button>
        </p>
    </form>
    <?php return ob_get_clean();
}
add_shortcode("basic_contact_form", "basic_contact_form_shortcode");