I am new to php and I am trying to display a value ($total_discount) to a textbox when radio button is clicked. But whenever my radio button is clicked, it only outputs a text 'undefined'. This is my code

<script type="text/javascript">
   function insertDiscount(getDiscount) {
      document.getElementById("discount").value = getDiscount;
   }
</script>

<?php
   $quantity = $_POST["quantity"];
   $discount_a = 0.10;
   $discounted_price;
   $total_discount;

   if(isset($item_price)){
       $discounted_price = $item_price * $discount_a;
       $total_discount = $discounted_price * $quantity;
   }
?>

<input type="text" name="discount" id="discount" value="">
<input type="radio" name="discounts" id="discount_A" onclick="insertDiscount(''.$total_discount);">
<label for="discount_A">10% Discount</label>

CodePudding user response：

<input type="radio" name="discounts" id="discount_A" onclick="insertDiscount(''.$total_discount);">

A few things need to change.

• Since you have the insertDiscount() with the () it is called immediately and not onclick
  • You need to use insertDiscount.bind(this, variable)
• Next, to output the value of $total_discount you need to <?= $total_discount; ?> which will echo the value

So your final result will look something like this.

onclick="insertDiscount.bind(this, '<?= $total_discount; ?>'">

CodePudding user response：

PHP is not rendering the value of the variable $total_discount.

Chanage

onclick="insertDiscount(''.$total_discount);"

to

onclick="insertDiscount(<?php echo($total_discount); ?>)"

to achieve the desired result.