Wordpress category functions using YOAST

WP useful category functions

function get_primary_category() {
    $category = get_the_category();
    $useCatLink = true;

    /* if( in_array( 'wordpress-seo/wp-seo.php', apply_filters( 'active_plugins', get_option('active_plugins') ) ) ) */
    if ($category) {
        $category_display = '';
        $category_link = '';
        if ( class_exists('WPSEO_Primary_Term') ) {
            $wpseo_primary_term = new WPSEO_Primary_Term( 'category', get_the_id() );
            $wpseo_primary_term = $wpseo_primary_term->get_primary_term();
            $term = get_term( $wpseo_primary_term );
            if (is_wp_error($term)) {
                $category_display = $category[0]->name;
                $category_link = get_category_link( $category[0]->term_id );
            } else { 
                $category_display = $term->name;
                $category_link = get_category_link( $term->term_id );
            }
        } else {
            $category_display = $category[0]->name;
            $category_link = get_category_link( $category[0]->term_id );
        }
        if ( !empty($category_display) ){
            if ( $useCatLink == true && !empty($category_link) ){
                //echo '<a href="'.$category_link.'">'.htmlspecialchars($category_display).'</a>';
                return htmlspecialchars($category_display);
            } else {
                return htmlspecialchars($category_display);
            }
        }
    }
}

// Display primary category slug for redirection
function get_primary_category_slug() {
    $category = get_the_category();
    $useCatLink = true;
    if ($category) {
        $category_display = '';
        $category_link = '';
        if ( class_exists('WPSEO_Primary_Term') ) {
            $wpseo_primary_term = new WPSEO_Primary_Term( 'category', get_the_id() );
            $wpseo_primary_term = $wpseo_primary_term->get_primary_term();
            $term = get_term( $wpseo_primary_term );
            if (is_wp_error($term)) { 
                $category_display = $category[0]->slug;
                $category_link = get_category_link( $category[0]->term_id );
            } else { 
                $category_display = $term->slug;
                $category_link = get_category_link( $term->term_id );
            }
        } else {
            $category_display = $category[0]->slug;
            $category_link = get_category_link( $category[0]->term_id );
        }
        if ( !empty($category_display) ){
            if ( $useCatLink == true && !empty($category_link) ){
                return htmlspecialchars($category_display);
            } else {
                return htmlspecialchars($category_display);
            }
        }
    }
}

/* If you are using a custom field from the primary category */
function get_primary_category_color() {
    $category = get_the_category();
    if ($category) {
        if ( class_exists('WPSEO_Primary_Term') ) {
            $wpseo_primary_term = new WPSEO_Primary_Term( 'category', get_the_id() );
            $wpseo_primary_term = $wpseo_primary_term->get_primary_term();
            $term = get_term( $wpseo_primary_term );
            return get_field('category-color', 'term_'.$term->term_id);
        } else {
            return get_field('category-color', 'term_'.get_the_id());
        }
    }
}