add_action( 'quick_edit_custom_box', 'display_ir_quickedit_cena', 10, 2 );

function display_ir_quickedit_cena( $column_name, $post_type ) {
    static $printNonce = TRUE;
    if ( $printNonce ) {
        $printNonce = FALSE;
        wp_nonce_field( 'ir_edit_cena', 'ir_darky_edit_nonce' );
    }

    ?>
    <fieldset class="inline-edit-col-right inline-edit-cena">
      <div class="inline-edit-col column-<?php echo $column_name; ?>">
        <label class="inline-edit-group">
        <?php
         switch ( $column_name ) {
         case 'cena':
             ?><span class="title">Cena v kreditech</span><input name="cena" /><?php
             break;
         }
        ?>
        </label>
      </div>
    </fieldset>
    <?php
}

add_action( 'save_post', 'save_cena_meta' );

function save_cena_meta( $post_id ) {
    /* in production code, $slug should be set only once in the plugin,
       preferably as a class property, rather than in each function that needs it.
     */
    $slug = 'ir_darky';
    if ( $slug !== $_POST['post_type'] ) {
        return;
    }
    if ( !current_user_can( 'edit_post', $post_id ) ) {
        return;
    }
    $_POST += array("{$slug}_edit_nonce" => '');
    if ( !wp_verify_nonce( $_POST["{$slug}_edit_nonce"],
        'ir_edit_cena' ) )
    {
        return;
    }

    if ( isset( $_REQUEST['cena'] ) ) {
        update_post_meta( $post_id, 'kbnt_cena', $_REQUEST['cena'] );
    }
}

/* load script in the footer */
if ( ! function_exists('wp_ir_admin_enqueue_scripts') ):
function wp_ir_admin_enqueue_scripts( $hook ) {

    if ( 'edit.php' === $hook &&
        isset( $_GET['post_type'] ) &&
        'ir_darky' === $_GET['post_type'] ) {

        wp_enqueue_script( 'ir_custom_script', get_stylesheet_directory_uri().'/js/admin_edit.js',
            false, null, true );
    }

}
endif;
add_action( 'admin_enqueue_scripts', 'wp_ir_admin_enqueue_scripts' );


/* example of how an existing value can be stored in the table */
add_action( 'manage_cena_posts_custom_column' , 'custom_cena_column', 10, 2 );
function custom_cena_column( $column, $post_id ) {
    switch ( $column ) {
      case 'cena':
        // the !! means translate the following item to a boolean value
        if ( !!get_post_meta( $post_id , 'kbnt_cena' , true ) ) {
            $value = get_post_meta( $post_id , 'kbnt_cena' , true );
        }
        echo '<span class="title">Cena v kreditech</span><input name="cena" value="'.$value.'"/>';
        break;
    }
}