When we create or update a product, if the SKU (_sku) field has less than 13 digits, we have to fill in zeros to always reach 13 digits.

• For instance, if the field contains nothing, then we should add 13 zeros in the field.

• For instance, if the field contains 123456, then we should add 7 zeros before it.

• For instance, if the field contains 123456789, then we should add 3 zeros before it.

• For instance, if the field contains 1234567891234, then we should do nothing because it has 13 digits.

I have the below code, which partially works, meaning that it effectively adjust the number of digits in the backend, but when I search for the product based on SKU in the frontend, I’m not finding the product, so I guess that it doesn’t work fine. Any one to help on this? Thanks

function ensure_13_digit_sku($sku) {
    return str_pad($sku, 13, '0', STR_PAD_LEFT);
}
function ensure_sku_length_on_save($post_id, $post, $update) {
    if ($post->post_type !== 'product') {
        return;
    }
    $sku = get_post_meta($post_id, '_sku', true);
    if (!$sku || strlen($sku) < 13) {
        $new_sku = ensure_13_digit_sku($sku);
        update_post_meta($post_id, '_sku', $new_sku);
    }
}
add_action('save_post', 'ensure_sku_length_on_save', 10, 3);