file upload

function brush_packs() {
  $labels = array(
    'name'               => _x( 'Brush Packs', 'post type general name' ),
    'singular_name'      => _x( 'Brush Pack', 'post type singular name' ),
    'add_new'            => _x( 'Add New', 'brushes' ),
    'add_new_item'       => __( 'Add New Brush Pack' ),
    'edit_item'          => __( 'Edit Brush Pack' ),
    'new_item'           => __( 'New Brush Pack' ),
    'all_items'          => __( 'All Brushes' ),
    'view_item'          => __( 'View Brushes' ),
    'search_items'       => __( 'Search Brushes' ),
    'not_found'          => __( 'No Brushes found' ),
    'not_found_in_trash' => __( 'No Brushes found in the Trash' ),
    'parent_item_colon'  => '',
    'menu_name'          => 'Brushes'
  );
  $args = array(
    'labels'        => $labels,
    'description'   => 'text',
    'public'        => true,
    'menu_position' => 5,
    'menu_icon' => 'dashicons-admin-customizer',
    'supports'      => array( 'title', 'thumbnail'),
    'has_archive'   => true,
  );
  register_post_type( 'brushes', $args );
}
add_action( 'init', 'brush_packs' );

function brushes_taxonomy() {
    register_taxonomy(
        'brushes_categories',  //The name of the taxonomy. Name should be in slug form (must not contain capital letters or spaces).
        'brushes',        //post type name
        array(
            'hierarchical' => true,
            'label' => 'Brush Types',  //Display name
            'query_var' => true,
            'rewrite' => array(
                'slug' => 'brushes', // This controls the base slug that will display before each term
                'with_front' => false // Don't display the category base before
            )
        )
    );
}
add_action( 'init', 'brushes_taxonomy');


function add_custom_meta_boxes() {

    // Define the custom attachment for posts
    add_meta_box(
        'brush_pack_attachment',
        'Custom Attachment',
        'brush_pack_attachment',
        'brushes',
        'normal'
    );

} // end add_custom_meta_boxes
add_action('add_meta_boxes', 'add_custom_meta_boxes');

function brush_pack_attachment() {

    wp_nonce_field(plugin_basename(__FILE__), 'brush_pack_attachment_nonce');

    $html = '<p class="description">';
        $html .= 'Upload your PDF here.';
    $html .= '</p>';
    $html .= '<input type="file" id="brush_pack_attachment" name="brush_pack_attachment" value="" size="25" />';

    echo $html;

} // end brush_pack_attachment

function save_custom_meta_data($id) {

    /* --- security verification --- */
    if(!wp_verify_nonce($_POST['brush_pack_attachment_nonce'], plugin_basename(__FILE__))) {
      return $id;
    } // end if

    if(defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
      return $id;
    } // end if

    if('brushes' == $_POST['post_type']) {
      if(!current_user_can('edit_page', $id)) {
        return $id;
      } // end if
    } else {
        if(!current_user_can('edit_page', $id)) {
            return $id;
        } // end if
    } // end if
    /* - end security verification - */

    // Make sure the file array isn't empty
    if(!empty($_FILES['brush_pack_attachment']['name'])) {

        // Setup the array of supported file types. In this case, it's just PDF.
        $supported_types = array('application/pdf');

        // Get the file type of the upload
        $arr_file_type = wp_check_filetype(basename($_FILES['brush_pack_attachment']['name']));
        $uploaded_type = $arr_file_type['type'];

        // Check if the type is supported. If not, throw an error.
        if(in_array($uploaded_type, $supported_types)) {

            // Use the WordPress API to upload the file
            $upload = wp_upload_bits($_FILES['brush_pack_attachment']['name'], null, file_get_contents($_FILES['brush_pack_attachment']['tmp_name']));

            if(isset($upload['error']) && $upload['error'] != 0) {
                wp_die('There was an error uploading your file. The error is: ' . $upload['error']);
            } else {
                add_post_meta($id, 'brush_pack_attachment', $upload);
                update_post_meta($id, 'brush_pack_attachment', $upload);
            } // end if/else

        } else {
            wp_die("The file type that you've uploaded is not a PDF.");
        } // end if/else

    } // end if

} // end save_custom_meta_data
add_action('save_post', 'save_custom_meta_data');

function update_edit_form() {
    echo ' enctype="multipart/form-data"';
} // end update_edit_form
add_action('post_edit_form_tag', 'update_edit_form');