在当前表中插入数据并更新另一个表MySQL

I'm having problem with inserting in purchase table and updating facility table. Let's say, user made a purchase with product_id and product_quantity.

The query is running. But it inserts twice with the same data and not updating facility table.

When user hit submit, I want to insert product_id and product_quantity into purchase table. And updating facility table with product_id and product_quantity that associated with it.

Here is my code

<?php
include 'dbconn.inc.php';
include 'functions.inc.php';

 $sql1 = "SELECT * FROM facilities";

 $res = $mysqli->query($sql1);
 $facilities = array();

 while( $row = $res->fetch_array(MYSQLI_ASSOC) ){

 $facilities[]['id'] = $facilities_id;
 $facilities[]['product_id'] = $facilities_product_id;
 $facilities[]['product_current_quantity'] = $product_current_quantity;
}


 $id = $mysqli->real_escape_string ($_POST['id']);
 $purchase_id = $mysqli->real_escape_string( $_POST['purchase_id'] );
 $facility_id = $mysqli->real_escape_string( $_POST['facility_id'] );
 $product_quantity = $mysqli->real_escape_string( $_POST['product_quantity'] );



 $sql1 = "UPDATE facilities
 SET

 `product_current_quantity` = '$product_quantity + $product_current_quantity'


 WHERE $facility_id = $facilities_id AND $id = $facilities_product_id ";


 $sql = "INSERT INTO purchases
 (
 `purchase_id`,
 `facility_id`, 
 `product_quantity`,,
  `product_id`
  )
  VALUES
  (

  '$purchase_id',
  '$facility_id',
  '$product_quantity',
  '$id'

   )";

I did some research and I think I need to use triggers. But I never work with triggers before. Any helps would be great. Thank you!

Please execute your query and better use echo statement if you have doubt in query. use "php.net"

used this code to your updates

product_current_quantity = product_current_quantity + $product_current_quantity 

how many number they can add to your product Quantity and they sum the current number.

You have used insert query and update query for the same variable $sql without any condition. If so always your following query only executes. Then anymore no update only insertion will reflect in your table.

$sql = "INSERT INTO purchases
 (
 `purchase_id`,
 `facility_id`, 
 `product_quantity`,,
  `product_id`
  )
  VALUES
  (

  '$purchase_id',
  '$facility_id',
  '$product_quantity',
  '$id'

   )";