Advanced Custom Field on Front-end

// =====================================================================================
// UPDATE: A better method for both frontend submission and editing is available here
// https://itsmereal.com/frontend-post-submission-edit-advanced-custom-fields/
// =====================================================================================


// ======================================================================================
// Codes to put on your page template header
// Remember, the above piece of code needs to be placed between <?php and get_header();
// ======================================================================================

**
 * Add required acf_form_head() function to head of page
 * @uses Advanced Custom Fields Pro
 */
add_action( 'get_header', 'tsm_do_acf_form_head', 1 );
function tsm_do_acf_form_head() {
    // Bail if not logged in or not able to post
    if ( ! ( is_user_logged_in() || current_user_can('publish_posts') ) ) {
        return;
    }
    acf_form_head();
}

/**
 * Deregister the admin styles outputted when using acf_form
 */
add_action( 'wp_print_styles', 'tsm_deregister_admin_styles', 999 );
function tsm_deregister_admin_styles() {
    // Bail if not logged in or not able to post
    if ( ! ( is_user_logged_in() || current_user_can('publish_posts') ) ) {
        return;
    }
    wp_deregister_style( 'wp-admin' );
}

// ======================================================================================
// Codes to put on your content body area
// ======================================================================================


// Bail if not logged in or able to post
    if ( ! ( is_user_logged_in()|| current_user_can('publish_posts') ) ) {
        echo '<p>You must be a registered author to post.</p>';
        return;
    }

    $new_post = array(
        'post_id'            => 'new', // Create a new post
        // PUT IN YOUR OWN FIELD GROUP ID(s)
        'field_groups'       => array(7,58), // Create post field group ID(s)
        'form'               => true,
        'return'             => '%post_url%', // Redirect to new post url
        'html_before_fields' => '',
        'html_after_fields'  => '',
        'submit_value'       => 'Submit Post',
        'updated_message'    => 'Saved!'
    );
    acf_form( $new_post );


// ======================================================================================
// Codes to put on your functions.php file
// ======================================================================================


/**
 * Back-end creation of new candidate post
 * @uses Advanced Custom Fields Pro
 */
add_filter('acf/pre_save_post' , 'tsm_do_pre_save_post' );
function tsm_do_pre_save_post( $post_id ) {

    // Bail if not logged in or not able to post
    if ( ! ( is_user_logged_in() || current_user_can('publish_posts') ) ) {
        return;
    }

    // check if this is to be a new post
    if( $post_id != 'new' ) {
        return $post_id;
    }

    // Create a new post
    $post = array(
        'post_type'     => 'post', // Your post type ( post, page, custom post type )
        'post_status'   => 'publish', // (publish, draft, private, etc.)
        'post_title'    => wp_strip_all_tags($_POST['acf']['field_54dfc93e35ec4']), // Post Title ACF field key
        'post_content'  => $_POST['acf']['field_54dfc94e35ec5'], // Post Content ACF field key
    );

    // insert the post
    $post_id = wp_insert_post( $post );

    // Save the fields to the post
    do_action( 'acf/save_post' , $post_id );

    return $post_id;

}

/**
 * Save ACF image field to post Featured Image
 * @uses Advanced Custom Fields Pro
 */
add_action( 'acf/save_post', 'tsm_save_image_field_to_featured_image', 10 );
function tsm_save_image_field_to_featured_image( $post_id ) {

    // Bail if not logged in or not able to post
    if ( ! ( is_user_logged_in() || current_user_can('publish_posts') ) ) {
        return;
    }

    // Bail early if no ACF data
    if( empty($_POST['acf']) ) {
        return;
    }

    // ACF image field key
    $image = $_POST['acf']['field_54dfcd4278d63'];

    // Bail if image field is empty
    if ( empty($image) ) {
        return;
    }

    // Add the value which is the image ID to the _thumbnail_id meta data for the current post
    add_post_meta( $post_id, '_thumbnail_id', $image );

}