Add a select field that will change price in Woocommerce simple products

Question

I need to add a select with a custom price in the single product as seen in the screenshots below;

The idea is that by selecting an option from (select) you can increase it to the base price.

Without using the variations, since my idea is to do other things more, but I need help on how to do this.

I've seen plugins that do it are called "Add-On" but I do not want to use a plugin.

Answer 1

To add a select field in simple products (like in variable products) that will update base price depending on the dopdown selected value, try this:

// Frontend: custom select field in product single pages
add_action( 'woocommerce_before_add_to_cart_button', 'fabric_length_product_field' );
function fabric_length_product_field() {
    global $product;

    if( $product->is_type('variable') ) return; // Not variable products

    $domain = 'woocommerce';
    $text   = array(
        __('cards', $domain),
        __('card', $domain),
        __('Total', $domain),
        get_woocommerce_currency_symbol(),
    );

    // Select Options array
    $options = array(
        ""          => __('Select package'),
        "12.00" => "1000 {$text[0]} - {$text[3]}0.012/{$text[1]} - {$text[2]} {$text[3]}12.00",
        "15.00" => "2000 {$text[0]} - {$text[3]}0.008/{$text[1]} - {$text[2]} {$text[3]}15.00",
        "20.00" => "3000 {$text[0]} - {$text[3]}0.007/{$text[1]} - {$text[2]} {$text[3]}20.00",
        "25.00" => "4000 {$text[0]} - {$text[3]}0.006/{$text[1]} - {$text[2]} {$text[3]}25.00",
    );

    // Select field
    woocommerce_form_field('cards_pack', array(
        'type'          => 'select',
        'class'         => array('my-field-class form-row-wide'),
        'label'         => __('Cards Pack selection', $domain),
        'required'      => true,
        'options'       => $options,
    ),'');

    // Data to be transmitted to jQuery
    $base_price = (float) wc_get_price_to_display( $product );
    $prices = array(
        ''      => wc_price($base_price),
        '12.00' => wc_price($base_price + 12),
        '15.00' => wc_price($base_price + 15),
        '20.00' => wc_price($base_price + 20),
        '25.00' => wc_price($base_price + 25),
    )

    // jQuery code
    ?>
    <script>
    jQuery(function($){
        var a = <?php echo json_encode($prices); ?>,
            b = 'p.price',
            c = 'select[name="cards_pack"]';

        $(c).on( 'change', function(){
            $.each( a, function( key, value ){
                if( $(c).val() == key )
                    $(b).html(value);
            });
        });
    });
    </script>
    <?php
}

// Add selected pack data as custom data to cart items
add_filter( 'woocommerce_add_cart_item_data', 'add_pack_data_to_cart_item_data', 20, 2 );
function add_pack_data_to_cart_item_data( $cart_item_data, $product_id ){
    if( ! isset($_POST['cards_pack']) )
        return $cart_item_data;

    $pack_price = (float) sanitize_text_field( $_POST['cards_pack'] );
    if( empty($pack_price) )
        return $cart_item_data;

    if($pack_price == 12.00) $cards = 1000;
    elseif($pack_price == 15.00) $cards = 2000;
    elseif($pack_price == 20.00) $cards = 3000;
    elseif($pack_price == 25.00) $cards = 4000;

    $product    = wc_get_product($product_id); // The WC_Product Object
    $base_price = (float) $product->get_price();

    // New price calculation
    $new_price = $base_price + $pack_price;

    // Prepare and save the data array
    $cart_item_data['pack_data'] = array(
        'cards'     => (int)   $cards,
        'pack'      => (int)   $pack_price,
        'new_price' => (float) $new_price,
    );
    $cart_item_data['unique_key'] = md5( microtime() . rand() ); // Make each item unique

    return $cart_item_data;
}

// Set conditionally a custom item price
add_action('woocommerce_before_calculate_totals', 'set_cutom_cart_item_price', 20, 1);
function set_cutom_cart_item_price( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 )
        return;

    foreach (  $cart->get_cart() as $cart_item ) {
        if ( isset( $cart_item['pack_data']['new_price'] ) )
            $cart_item['data']->set_price( $cart_item['pack_data']['new_price'] );
    }
}


// Display custom data in  checkout page
add_filter( 'woocommerce_get_item_data', 'display_custom_cart_item_data', 10, 2 );
function display_custom_cart_item_data( $cart_data, $cart_item ) {
    $domain        = 'woocommerce';

    if ( isset( $cart_item['pack_data']['new_price'] ) ){
        $cart_data[] = array('name' => __( 'Cards pack', $domain ),
            'value' => $cart_item['pack_data']['cards'] );
    }
    return $cart_data;
}

Code goes in function.php file of your active child theme (or active theme). Tested and work.