Woocoommerce modify product price

woo-modify-product-price.php

// Add to cart markup - added custom input field for event_id
$price = get_post_meta(get_the_ID(), 'price', true );
if( $price ) {
    echo '<form class="cart" action="" method="post" enctype="multipart/form-data">
        <div class="quantity">
            <label class="screen-reader-text" for="quantity_5beeab967f651">Quantity</label>
            <input type="number" id="quantity_5beeab967f651" class="input-text qty text" step="1" min="1" max="" name="quantity" value="1" title="Qty" size="4" pattern="[0-9]*" inputmode="numeric" aria-labelledby="">
        </div>
        <input type="hidden" name="event_id" value="'. get_the_ID() .'">
    <button type="submit" name="add-to-cart" value="119" class="single_add_to_cart_button button alt">Add to cart</button>
    </form>';
}

// On add to cart
function add_cart_item_data( $cart_item_data, $product_id, $variation_id ) {
    if( isset($_POST['event_id']) ){
        // add event id price to data
        $cart_item_data['event_price'] = get_post_meta((int)$_POST['event_id'], 'price', true);
    }
    return $cart_item_data;
}
add_filter( 'woocommerce_add_cart_item_data', 'add_cart_item_data', 10, 3 );

// Apply added data price
function before_calculate_totals( $cart_obj ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) ) {
        return;
    }
    // Iterate through each cart item
    foreach( $cart_obj->get_cart() as $key=>$value ) {
        if( isset( $value['event_price'] ) ) {
            $price = $value['event_price'];
            $value['data']->set_price( ( $price ) );
        }
    }
}
add_action( 'woocommerce_before_calculate_totals', 'before_calculate_totals', 10, 1 );