add_action( 'wp_ajax_tnet_load_post_content', 'tnet_load_post_content' );
add_action( 'wp_ajax_nopriv_tnet_load_post_content', 'tnet_load_post_content' );

function tnet_load_post_content() {

    $id = $_POST['pageId'];
    $meta = get_post_meta( $id, 'panels_data', true );

    if( class_exists( 'SiteOrigin_Panels' ) && $meta )
    {
        $renderer = SiteOrigin_Panels::renderer();
        $content = $renderer->render( $id );
        $css = $renderer->generate_css( $id );
    }
    else
    {
        $css = '';
        $content = apply_filters( 'the_content', get_page($id)->post_content );
    }

    echo json_encode(array($content, $css));
    die();
}