Primary Category Yoast 2

if ( !class_exists('WPSEO_Primary_Term') ) {
    $category_index = 0;
    foreach( $post->post_categories as $category ) {
        $category_index++;
        $separator =  $category_index < count(  $post->post_categories ) ? ', ' : '';
        echo '<a href="'. esc_url( $category['permalink'] ) .'" title="' . esc_attr( $category['label'] ) . '">' . esc_html( $category['label'] ) . '</a>' . $separator;
    }
} else {
    // SHOW YOAST PRIMARY CATEGORY, OR FIRST CATEGORY
    $category = $post->post_categories;
    $useCatLink = true;
    // If post has a category assigned.
    if ($category){
        $category_display = '';
        $category_link = '';

        // Show the post's 'Primary' category, if this Yoast feature is available, & one is set
        $wpseo_primary_term = new WPSEO_Primary_Term( 'project_category', get_the_id() );
        $wpseo_primary_term = $wpseo_primary_term->get_primary_term();
        $term = get_term( $wpseo_primary_term );
        if (is_wp_error($term)) {
            // Default to first category (not Yoast) if an error is returned
            $category_display = $category[0]->name;
            $category_link = get_category_link( $category[0]->term_id );
        } else {
            // Yoast Primary category
            $category_display = $term->name;
            $category_link = get_term_link( $term->term_id );
        }

        // Display category
        if ( !empty($category_display) ){
            if ( $useCatLink == true && !empty($category_link) ){
            echo '<a href="'.$category_link.'">'.htmlspecialchars($category_display).'</a>';
            } else {
            echo '<span class="post-category">'.htmlspecialchars($category_display).'</span>';
            }
        }

    }
}