WordPress subscription form

functions.php

wp_enqueue_script( 'gym-subscribe', get_template_directory_uri() . '/assets/js/subscribe-form.js', array('jquery'), THEME_VERSION, true );
wp_localize_script( 'gym-subscribe', 'subscribe_form_object', array(
  'url'   => admin_url( 'admin-ajax.php' ),
  'nonce' => wp_create_nonce( 'subscribe-form-nonce' ),
) );

subscribe-form-functions.php

<?php 

add_action( 'wp_ajax_subscribe_form_action', 'subscribe_action_callback' );
add_action( 'wp_ajax_nopriv_subscribe_form_action', 'subscribe_action_callback' );

function subscribe_action_callback() {

// errors array
$errors = [];

// checking nonce
if ( !wp_verify_nonce( $_POST['nonce'], 'subscribe-form-nonce' ) ) {
wp_die( esc_html__('Something went wrong') );
}

// checking spam
if ( $_POST['form_anticheck'] === false || !empty( $_POST['form_submitted'] ) ) {
wp_die( esc_html_e('Something went wrong') );
}

// checking mail field
if ( empty( $_POST['subscribe-form__email'] ) || !isset( $_POST['subscribe-form__email'] ) ) {
$errors['mail'] = esc_html__('Please enter your email');
} else {
$form_mail = sanitize_text_field( $_POST['subscribe-form__email'] );
}

// checking errors array
if ( $errors ) {

wp_send_json_error( $errors );

} else {

// checking from which site is mail
$home_url = wp_parse_url( home_url() );
$subject = esc_html__('Mail from') . ' ' .  $home_url['host'];

// mail headers
$email_to = 'marstamyan@mail.ru';
$email_from = get_option( 'admin_email' );

// mail content
$body = esc_html__('Email:') . $form_mail . '<br>';

$headers = 'From: ' . $home_url['host'] . ' <' . $email_from . '>' . "<br>" . 'Reply-To: ' . $email_from;

// sending mail
wp_mail( $email_to, $subject, $body, $headers );

/* adding mail data into custom post type post */
$post_data = array(
    'post_title'    => $form_mail,
    'post_status'   => 'publish',
    'post_author'   => 1,
    'post_type' => 'subscription',
   );
 
wp_insert_post( $post_data );

// showing message if mail is sended
$message_success = esc_html__('Thanks for your subscription');
    wp_send_json_success( $message_success );
}

wp_die();

}

subscribe-form.js

jQuery(document).ready(function ($) {
    var form = $('#subscribe-form');
     
    $('#subscribe-form input').on('click', function () {
        $('#subscribe-form input').removeClass('error');
        $('.notification').remove();
        $('#subscribe-form__btn').val('Subscribe');
        
    });

    var options = {
        url: subscribe_form_object.url,
        data: {
            action: 'subscribe_form_action',
            nonce: subscribe_form_object.nonce
        },
        type: 'POST',
        dataType: 'json',
        beforeSubmit: function (xhr) {
            // changing button text
            $('#subscribe-form__btn').val('Subscribing...');
        },
        success: function (request, xhr, status, error) {

            if (request.success === true) {
                // cheking if fields filled — sending data and changing button text
                form.after('<div class="notification notification_accept">' + request.data + '</div>').slideDown();
                $('#subscribe-form__btn').val('Subscribe');               
            } else {
                // cheking if fields is empty and changing button text
                $.each(request.data, function (key, val) {
                    $('.form_' + key).addClass('error');
                    $('.form_' + key).after('<div class="notification notification_warning notification_warning_' + key + '">' + val + '</div>');
                });
                $('#subscribe-form__btn').val('Something went wrong...');
            }
            // reset form field if all is OK
            $('#subscribe-form')[0].reset();
        },
        error: function (request, status, error) {
            $('#subscribe-form__btn').val('Something went wrong...');
        }
    };
    // form sending
    form.ajaxForm(options);
});