So...here is part of my code for a plugin. I'm a newb of sorts so be kind. I've read up on global variables but I can't seem to get it to work and I've read you shouldn't use them anyway. So what would be the best way to write the code below without having to re-declare the variables for each function? Here is the full code if necessary.

// Display the product badge on the shop page

add_action( 'woocommerce_after_shop_loop_item_title', 'wc_simple_product_badge_display_shop', 30 );
function wc_simple_product_badge_display_shop() {
    $title = get_post_meta( get_the_ID(), '_wc_simple_product_badge_title', true ); // badge title
    $class = get_post_meta( get_the_ID(), '_wc_simple_product_badge_class', true ); // badge class
    $duration = get_post_meta( get_the_ID(), '_wc_simple_product_badge_duration', true ); // badge duration
    $postdate = get_the_time( 'Y-m-d' ); // post date
    $postdatestamp = strtotime( $postdate ); // post date in unix timestamp
    $difference = round ((time() - $postdatestamp) / (24*60*60));  // difference in days between now and product's post date

    if ( !empty( $title ) && empty( $duration ) || !empty( $title ) && $difference <= $duration ){ // Check to see if there is a title and the product is still within the duration timeframe if specified
        $class = !empty( $class ) ? $class : '';
        echo '<span class="wc_simple_product_badge ' . $class . '">' . $title . '</span>';
    }
}

// Display the product badge on the single page

add_filter( 'woocommerce_single_product_image_html', 'wc_simple_product_badge_display_single' );    
function wc_simple_product_badge_display_single( $img_html ) {
    $title = get_post_meta( get_the_ID(), '_wc_simple_product_badge_title', true ); // badge title
    $class = get_post_meta( get_the_ID(), '_wc_simple_product_badge_class', true ); // badge class
    $duration = get_post_meta( get_the_ID(), '_wc_simple_product_badge_duration', true ); // badge duration
    $single_opt = get_post_meta( get_the_ID(), '_wc_simple_product_badge_single_page_option', true ); // badge on single page
    $postdate = get_the_time( 'Y-m-d' ); // post date
    $postdatestamp = strtotime( $postdate ); // post date in unix timestamp
    $difference = round ((time() - $postdatestamp) / (24*60*60));  // difference in days between now and product's post date
    
    if ( !empty( $title ) && empty( $duration ) && $single_opt === 'yes' || !empty( $title ) && $difference <= $duration && $single_opt === 'yes' ){ // Check to see if there is a title and the product is still within the duration timeframe ()if specified) and the checkbox is checked to show on single page view
        $class = !empty( $class ) ? $class : '';
        echo '<span class="wc_simple_product_badge ' . $class . '">' . $title . '</span>';
        return $img_html;
}

    elseif ( $single_opt === 'no' ) { // Check to see if the checkbox is unchecked to show on single page view
        return $img_html;
    }

}