Conditional display of css container - php

Question

EDIT : I use return true; in the first function and if(fonction1() === true) in the second.
However it displays me the boolean value at the front-end, namely "1". Any idea how not to display this?
I'm trying to do this with this code:
Here is my code with my try but it doesn't work (the "if" "else" should just allow to change the associated css class)
// Sales badge
add_action( 'woocommerce_sale_flash', 'sale_badge_percentage', 25 );
function sale_badge_percentage() {
global $product;
if ( ! $product->is_on_sale() ) return;
if ( $product->is_type( 'simple' ) ) {
$max_percentage = ( ( $product->get_regular_price() - $product->get_sale_price() ) / $product->get_regular_price() ) * 100;
} elseif ( $product->is_type( 'variable' ) ) {
$max_percentage = 0;
foreach ( $product->get_children() as $child_id ) {
$variation = wc_get_product( $child_id );
$price = $variation->get_regular_price();
$sale = $variation->get_sale_price();
if ( $price != 0 && ! empty( $sale ) ) $percentage = ( $price - $sale ) / $price * 100;
if ( $percentage > $max_percentage ) {
$max_percentage = $percentage;
}
}
}
if ( $max_percentage > 0 ) {
echo "<span class='onsale'>-" . round($max_percentage) . "%</span>";
return true;
}
}
// New badge for recent products
add_action( 'woocommerce_before_shop_loop_item_title', 'new_badge', 3 );
function new_badge() {
if(sale_badge_percentage() === true) {
/* la variable existe */
global $product;
$newness_days = 30; // Number of days the badge is shown
$created = strtotime( $product->get_date_created() );
if ( ( time() - ( 60 * 60 * 24 * $newness_days ) ) < $created ) {
echo '<span class="ct-woo-card-extra new-badge">' . esc_html__( 'NEW', 'woocommerce' ) . '</span>';
}
}
else {
/* la variable n'existe pas */
global $product;
$newness_days = 30; // Number of days the badge is shown
$created = strtotime( $product->get_date_created() );
if ( ( time() - ( 60 * 60 * 24 * $newness_days ) ) < $created ) {
echo '<span class="ct-woo-card-extra new-badge solobadge">' . esc_html__( 'NEW', 'woocommerce' ) . '</span>';
}
}
}