php - WooCommerce - Sum of product_id values -

i trying sum of specific product_id values in woocommerce assigned bacs payment gateway id. have array product id's , using array_sum sum of product values not working correctly. if lead me in better direction appreciated.

add_action('woocommerce_before_cart_total', 'invoice_price');  <?php $available_gateways = $woocommerce->payment_gateways->get_available_payment_gateways(); $product = new wc_product( get_the_id() ); $invoiceitems = array(522, 550, 523); $formatted_total = woocommerce_price( $this->order_total );  function invoice_price( $available_gateways ) {   if ( $available_gateways == $gateways['bacs'] ) {     foreach($product == in_array($values['product_id'])) {          echo array_sum($invoiceitems);     }     $invoicetotal = $formatted_total - $invoiceitems; } echo $invoicetotal(); } ?> 

consider following:

having array of 100, 200, , 300 add 600.

$formatted_total = 5000;

i substract $formatted_total $invoiceitems array, 5000 minus 600 equals 4400.

<?php  $invoiceitems = array(100, 200, 300);  $formatted_total = 5000;  $invoicetotal = $formatted_total - array_sum($invoiceitems);  echo $invoicetotal; // echo 4400  ?> 

echo $invoicetotal(); render invalid because trying echo invalid function.

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if use following:

$invoicetotal = $formatted_total - $invoiceitems; 

will produce following error:

fatal error: unsupported operand types