excerpt from wordpress header.php to have it get a category based header image

header_excerpt.php

 <?PHP
   // Check if this is a post or page, if it has a thumbnail, and if it's a big one
    if ( is_singular() &&
            has_post_thumbnail( $post->ID ) &&
            ( /* $src, $width, $height */ $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), array( HEADER_IMAGE_WIDTH, HEADER_IMAGE_WIDTH ) ) ) &&
            $image[1] >= HEADER_IMAGE_WIDTH ) :
        // Houston, we have a new header image!
        echo get_the_post_thumbnail( $post->ID, 'post-thumbnail' );
  //--- Added to have blog category page headings						
  elseif( is_category() ) : 
        $cat = get_query_var('cat');
        $yourcat = get_category ($cat);
        
        $src = get_stylesheet_directory_uri().'/images/headers/'.$yourcat->slug.'_header.jpg';
        $loc = get_stylesheet_directory().'/images/headers/'.$yourcat->slug.'_header.jpg';
        $dflt = get_stylesheet_directory_uri().'/images/headers/blog_header.jpg';                        

        if (file_exists($loc)) :                        
            echo '<img src="'.$src.'" width"'.HEADER_IMAGE_WIDTH.'" height="'.HEADER_IMAGE_HEIGHT.'alt="" />'; 
        else :
            echo '<img src="'.$dflt.'" width"'.HEADER_IMAGE_WIDTH.'" height="'.HEADER_IMAGE_HEIGHT.'alt="" />';
        endif;    
  // end of blog category page headings 
  //--- Added to have posts show their category image if none other available.	
  elseif(is_single()) :
        $category = get_the_category();
        $kat = $category[0]->category_nicename;
        
        $src = get_stylesheet_directory_uri().'/images/headers/'.$kat.'_header.jpg';
        $loc = get_stylesheet_directory().'/images/headers/'.$kat.'_header.jpg';
        $dflt = get_stylesheet_directory_uri().'/images/headers/blog_header.jpg';

        if (file_exists($loc)) :                        
            echo '<img src="'.$src.'" width"'.HEADER_IMAGE_WIDTH.'" height="'.HEADER_IMAGE_HEIGHT.'alt="" />'; 
        else :
            echo '<img src="'.$dflt.'" width"'.HEADER_IMAGE_WIDTH.'" height="'.HEADER_IMAGE_HEIGHT.'alt="" />';
        endif;    
        
  // end of post category heading
  //------ blog home page setting
  elseif(is_home()) :
        echo '<img src="'.get_stylesheet_directory_uri().'/images/headers/blog_header.jpg" width"'.HEADER_IMAGE_WIDTH.'" height="'.HEADER_IMAGE_HEIGHT.'alt="" />';
  else : ?>
        <img src="<?php header_image(); ?>" width="<?php echo HEADER_IMAGE_WIDTH; ?>" height="<?php echo HEADER_IMAGE_HEIGHT; ?>" alt="" />
<?php endif; // end check for featured image or standard header ?>