Wordpress get_header_image and Nivo Slider Switching - PHP If Else Statement?

Okay so here's my issue. I want to be able to toggle between a custom header using get_header_image and Nivo Slider. At one point I had this working, having merged the code into a If...Elseif...Else statement. Now I can't replicate it. The current code d开发者_开发知识库isplay both the header image and the slider beneath it. Any help would be greatly appreciated.

<?php
// Check if this is a post or page, if it has a thumbnail, and if it's a big one
if( 
    is_singular() 
    && current_theme_supports('post-thumbnails') 
    && has_post_thumbnail( $post->ID ) 
    &&( /* $src, $width, $height */ $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'post-thumbnail' ) ) 
    && $image[1] >= HEADER_IMAGE_WIDTH 
) :
    // Houston, we have a new header image!
    echo get_the_post_thumbnail( $post->ID );
elseif ( get_header_image() ) : 
?>
    <img src="<?php header_image(); ?>" width="<?php echo HEADER_IMAGE_WIDTH; ?>" height="<?php echo HEADER_IMAGE_HEIGHT; ?>" alt="" />
<?php 
endif; 
?>

<div id="slider">
<?php
$tmp = $wp_query;
$wp_query = new WP_Query( array ('post_type'=>'page','post__in'=>array(1814)));
if(have_posts()) :
    while(have_posts()) :
        the_post();
?>
        <a href="<?php the_permalink(); ?>"><?php the_post_thumbnail('nivothumb'); ?></a>
<?php
    endwhile;
endif;

$wp_query = $tmp; 
?>
</div><!-- close #slider -->

<?php
if( 
    is_singular() 
    && current_theme_supports('post-thumbnails') 
    && has_post_thumbnail( $post->ID ) 
    &&( /* $src, $width, $height */ $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'post-thumbnail' ) ) 
    && $image[1] >= HEADER_IMAGE_WIDTH )
{
  echo get_the_post_thumbnail( $post->ID );
}
elseif ( get_header_image() )
{ ?>
    <img src="<?php header_image(); ?>" width="<?php echo HEADER_IMAGE_WIDTH; ?>" height="   <?php echo HEADER_IMAGE_HEIGHT; ?>" alt="" />
<?php } ?>