Sum of total amount group by date - php

Question

I am trying to create invoice, where I 1st insert date wise items to the invoice_item table with invoice_id, then finally insert invoice number with sum of Total amount in to 'invoice' table. now problem is i need to sum of amount group by date, please see code & image-
what i want--
https://ibb.co/F0pknxN
My database-
https://ibb.co/gmw7s4S
My code-
<table>
<thead>
<tr>
<th class="tm_width_3 tm_semi_bold tm_primary_color tm_gray_bg">Date/Date Range</th>
<th class="tm_width_4 tm_semi_bold tm_primary_color tm_gray_bg">Method(s)</th>
<th class="tm_width_2 tm_semi_bold tm_primary_color tm_gray_bg">Specification/Description</th>
<th class="tm_width_1 tm_semi_bold tm_primary_color tm_gray_bg">Unit</th>
<th class="tm_width_1 tm_semi_bold tm_primary_color tm_gray_bg">Rate</th>
<th class="tm_width_1 tm_semi_bold tm_primary_color tm_gray_bg">Qty</th>
<th class="tm_width_1 tm_semi_bold tm_primary_color tm_gray_bg">Gross Amount</th>
<th class="tm_width_1 tm_semi_bold tm_primary_color tm_gray_bg">Minimum Amount</th>
<th class="tm_width_2 tm_semi_bold tm_primary_color tm_gray_bg tm_text_right">Net Amount</th>
</tr>
</thead>
<tbody>
<?php
include('../connect.php');
$inv = $_GET['inv'];
$result4 = $db->prepare("SELECT * FROM invoice_item where invoice_id= :a");
$result4->bindParam(':a', $inv);
$result4->execute();
for ($i = 0; $row4 = $result4->fetch(); $i++) {
?>
<tr>
<td class="tm_width_3">
<?php echo $row4['date']; ?>
</td>
<td class="tm_width_2">
<?php echo $row4['radiation_source']; ?>
</td>
<td class="tm_width_4">
<?php echo $row4['description']; ?>
</td>
<td class="tm_width_1">
<?php echo $row4['unit']; ?>
</td>
<td class="tm_width_2">
<?php echo $row4['unit_price']; ?>
</td>
<td class="tm_width_2">
<?php echo $row4['qty']; ?>
</td>
<td class="tm_width_2">
<?php echo $row4['amount']; ?>
</td>
<td class="tm_width_2">
<?php echo $row4['miniamount']; ?>
</td>
<td class="tm_width_2 tm_text_right">
<?php echo $row4['netamount']; ?>
</td>
<tr>
<?php } ?>
</tbody>
</table>

Answer 1

As you have mentioned that the "problem is i need to sum of amount group by date",
I am assuming that you are referring to the Gross amount as the amount whose sum is needed upon grouping by date.You need an additional group by query:
select sum(amount) as netamount, count(amount) as invoice_count from invoice_item group by date;
in the above sql query, netamount will give you sum of amount grouped by date, and invoice_count with no.of invoices per group.
then loop the below code with the result of the above query.
<td class="tm_width_2 tm_text_right"><?php echo $row4['netamount']; ?></td>