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If you’re looking for a simple way to detect if a WordPress page belongs to a certain category, you can use a WordPress function called in_category(). In this example code below, the script will detect if a post belongs to the “news” category. If it does, it will send an output to the WordPress header. If it isn’t, it will send an alternate output.

function urr_add_to_header() 
{
  if ( in_category( 'news' )) 
  {
    echo '';
  } else {
    echo '';
  }
}
add_action( 'wp_head', 'urr_add_to_header', 100 );

It’s a simple function that has many uses. You can accomplish quite a bit with the in_category() function along with a few WordPress hooks.