Product tabs function.php

Hallo,
Ich habe in meinem Child-Theme product-tabs in die functions.php eingebaut, aber die ?nderungen werden nicht angezeigt, bzw nicht übernommen.

Wo liegt der Fehler ?

/**
* WooCommerce – Individuelles Produkt-Feld hinzufügen
*/

add_action( ‘woocommerce_product_options_general_product_data’, ‘add_custom_product_field’ );

function add_custom_product_field() {
woocommerce_wp_textarea_input(
array(
‘id’ => ‘_custom_tab_description’,
‘label’ => __( ‘Custom Tab Description’ )
)
);
}

add_action( ‘woocommerce_process_product_meta’, ‘save_custom_product_field’ );

function save_custom_product_field( $post_id ){

$custom_tab_description = $_POST[‘_custom_tab_description’];

if( !empty( $custom_tab_description ) ) :
update_post_meta( $post_id, ‘_custom_tab_description’, esc_html( $custom_tab_description ) );
endif;
}

/**
* WooCommerce – Individuelle Produkt-Tabs hinzufügen
*/

add_filter( ‘woocommerce_product_tabs’, ‘add_woocommerce_product_tabs’ );

function add_woocommerce_product_tabs( $tabs ) {
$tabs[‘custom_tab’] = array(
‘title’ => __( ‘New Product Tab’ ),
‘priority’ => 50,
‘callback’ => ‘new_product_tab_callback’
);

return $tabs;
}

function new_product_tab_callback() {
global $post;

echo wpautop( get_post_meta( $post->ID, ‘_custom_tab_description’, true ) );
}

/**
* WooCommerce – Individuelle Produkt-Tabs hinzufügen
*/

add_filter( ‘woocommerce_product_tabs’, ‘add_woocommerce_product_tabs’ );

function add_woocommerce_product_tabs( $tabs ) {
$tabs[‘custom_tab’] = array(
‘title’ => __( ‘New Product Tab’ ),
‘priority’ => 50,
‘callback’ => ‘new_product_tab_callback’
);

return $tabs;
}

function new_product_tab_callback() {
echo ‘New Product Tab’;
echo ‘Here\’s your new product tab.’;
}