My shortcode is showing up twice

Question

The Problem: I made a custom post type and a shortcode to display it's information. I have done this before and it has not been a problem. When I display this shortcode, the content of the shortcode repeats twice on the page.

The Code: I added these actions and functions to the bottom of the plugins main file (the one that starts as plugin-name.php in the boilerplate)

function custom_post_type() {

$labels = array(
    'name'                  => _x( 'Carousel ', 'Post Type General Name', 'text_domain' ),
    'singular_name'         => _x( 'Carousel', 'Post Type Singular Name', 'text_domain' ),
    'menu_name'             => __( 'Carousel', 'text_domain' ),
    'name_admin_bar'        => __( 'Carousel', 'text_domain' ),
    'archives'              => __( 'Carousel Archives', 'text_domain' ),
    'parent_item_colon'     => __( 'Parent Item:', 'text_domain' ),
    'all_items'             => __( 'All Posts', 'text_domain' ),
    'add_new_item'          => __( 'Add New', 'text_domain' ),
    'add_new'               => __( 'Add New', 'text_domain' ),
    'new_item'              => __( 'New Carousel', 'text_domain' ),
    'edit_item'             => __( 'Edit Carousel', 'text_domain' ),
    'update_item'           => __( 'Update Carousel', 'text_domain' ),
    'view_item'             => __( 'View Carousel', 'text_domain' ),
    'search_items'          => __( 'Search Featured Blogs', 'text_domain' ),
    'not_found'             => __( 'Not found', 'text_domain' ),
    'not_found_in_trash'    => __( 'Not found in Trash', 'text_domain' ),
    'featured_image'        => __( 'Featured Image', 'text_domain' ),
    'set_featured_image'    => __( 'Set featured image', 'text_domain' ),
    'remove_featured_image' => __( 'Remove featured image', 'text_domain' ),
    'use_featured_image'    => __( 'Use as featured image', 'text_domain' ),
    'insert_into_item'      => __( 'Insert into item', 'text_domain' ),
    'uploaded_to_this_item' => __( 'Uploaded to this item', 'text_domain' ),
    'items_list'            => __( 'Items list', 'text_domain' ),
    'items_list_navigation' => __( 'Items list navigation', 'text_domain' ),
    'filter_items_list'     => __( 'Filter items list', 'text_domain' ),
);
$args = array(
    'label'                 => __( 'Post Type', 'text_domain' ),
    'description'           => __( 'Post Type Description', 'text_domain' ),
    'labels'                => $labels,
    'supports'              => array( ),
    'taxonomies'            => array( 'category', 'post_tag' ),
    'hierarchical'          => false,
    'public'                => true,
    'show_ui'               => true,
    'show_in_menu'          => true,
    'menu_position'         => 5,
    'show_in_admin_bar'     => true,
    'show_in_nav_menus'     => true,
    'can_export'            => true,
    'has_archive'           => true,
    'exclude_from_search'   => false,
    'publicly_queryable'    => true,
    'capability_type'       => 'page',
    'menu_icon'                => 'dashicons-welcome-view-site',
);
register_post_type( 'zeebo-carousel', $args );

}

add_action( 'init', 'custom_post_type', 0 );


function carousel_shortcode_func( $atts ) {

$a = shortcode_atts( array(
'id' =>  false,
'foo' => 'something',
'bar' => 'something else',
), $atts );

ob_start();

?>

shortcode content here<br />

<?php

return ob_get_contents();

}
add_shortcode( 'carousel', 'carousel_shortcode_func' );

Actions I have Already Taken to Fix This:
1. Changed themes
2. Deactivated all other plugins
3. Rewrote the code
3. Google Search

How do I make the content only show once per shortcode?

Answer 1

This is more about php than wp, but ob_get_contents returns the buffer without clearing it. So you get your buffer content twice. Use ob_get_clean to erase the buffer on returning it.