increment the field with additions of new values - php

Question

I have a phpscript which takes values (Manually entered) and inserts into the column in the database. Now I want to know how would I be adding new values to the existing values for the same card number entered.
if(isset($_POST['insert-btn'])){
#$cardnumber=$_POST['cardnumber'];
#$amount=$_POST['amount'];
if($cardnumber=="" || $amount==""){
echo '<script type="text/javascript">alert("Insert values in all fields")</script>';
}
else{
$query = "insert into Client_Details values('$cardnumber',$amount/2)";
$query_run=mysqli_query($con,$query);
if($query_run){
echo '<script type="text/javascript">alert("Values inserted successfully")</script>';
}
else{
echo '<script type="text/javascript">alert("Values not inserted successfully")</script>';
}
}
}
?>
For example , I have
card number: _________
Sale value: __________
Now for the same card number the sale value entered every different time should be added. If anybody can help me with that. It would be helpful.

Answer 1

Before you insert data into DB, check whether a record for the card number already exists in the DB.
If it exists, use UPDATE query else use INSERT query.
Try the below code:
<?php
if (isset($_POST['insert-btn']))
{
#$cardnumber = $_POST['cardnumber'];
#$amount = $_POST['amount'];
if ($cardnumber == "" || $amount == "")
{
echo '<script type="text/javascript">alert("Insert values in all fields")</script>';
}
else
{
$newQuery = mysqli_query($con, "SELECT * FROM Client_Details WHERE cardnumber='" . $cardnumber . "'");
if (mysqli_num_rows($newQuery) > 0)
{
$query = "UPDATE Client_Details SET amount = amount + '" . $amount . "' WHERE cardnumber = '" . $cardnumber . "'";
}
else
{
$query = "INSERT into Client_Details values('$cardnumber',$amount/2)";
}
$query_run = mysqli_query($con, $query);
if ($query_run)
{
echo '<script type="text/javascript">alert("Values inserted successfully")</script>';
}
else
{
echo '<script type="text/javascript">alert("Values not inserted successfully")</script>';
}
}
}
*Modify the table name and column names accordingly