Change appearance based on category but post is in two main categories

Question

I want to change header and menu based on what category a post is listed in.

I could duplicate the post and assigned each of the two categories separately but this sounds messy and bleh.

The post/s in this example belong in both "pirtek" and "btcc".

http://www.talkativebroadcasting.co.uk/

but the posts with pirtek need to be styled with custom header etc. (and eventually custom menu...which makes me think perhaps I should just duplicate for easy implementation of a seperate menu?)

What do you think? As it stands my standard header is prioritised every time

    <php
if ( has_category('pirtek') ) {
  $header = 'http://www.talkativebroadcasting.co.uk/wp-content/uploads/2013/11/cropped-pirtekheader.png'
} else {
  $header = 'http://talkativebroadcasting.co.uk/wp-content/uploads/2013/06/cropped-talkativeheader2.png'
}
?>

Answer 1

One easy way is to use has_category function.

E.g. in your header you can use

if ( has_category('pirtek') ) {
  $header = '/path/to/pirtek/header'
} else {
  $header = '/path/to/standard/header'
}

If the post has the 'kirtek' category, then the condition inside if is true, no matter what other categories the post belongs to.

This kind of if statement can be used everywhere you need, however, the snippet above works well in singular templates and inside the loop. If you want to use that conditional outside the loop, you need to pass the post object as second argument of has_category.

$postid = 10;

if ( has_category( get_post($postid) ) ) {
  // do something 
}

Answer 2

<?php 
if ( has_category('pirtek') ) {
$header_image = "http://www.talkativebroadcasting.co.uk/wp-content/uploads/2013/11/cropped-pirtekheader.png";
        if ( ! empty( $header_image ) ) : ?>
            <a href="<?php echo esc_url( "http://www.pirtek.co.uk/" ); ?>"><img src="<?php echo esc_url( $header_image ); ?>" class="header-image" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="" /></a>
        <?php endif; }

else {
$header_image = "http://talkativebroadcasting.co.uk/wp-content/uploads/2013/06/cropped-talkativeheader2.png";
        if ( ! empty( $header_image ) ) : ?>
            <a href="<?php echo esc_url( home_url( '/' ) ); ?>"><img src="<?php echo esc_url( $header_image ); ?>" class="header-image" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="" /></a>
        <?php endif; }

?>

For reference this code in header.php does exactly what I need. Many thanks!