Adding different values together from same table - php

Question

I have a table. In that table, there is are two fields called to and amount. I need to display the sum of amount of all rows where to value is equal to a particular value. (Say 34). How to achieve this?
Code I have done so far
$result = mysql_query("SELECT * FROM transactions WHERE to = '34'")or die(mysql_error());
while($row = mysql_fetch_array( $result )) { echo $row['amount']; } ?>
The above code gives the individual amount value of each row. But what I want is the sum of these values.
The Database

Answer 1

Use SUM to add all the amounts and echo it
$result = mysql_query("SELECT SUM(amount) as amounts FROM transactions WHERE to = '34'")or die(mysql_error());
while($row = mysql_fetch_array( $result )) { echo $row['amounts']; } ?>

Answer 2

I suggest you to use mysqli_* or PDO because mysql_* is deprecated and not available in PHP 7.
Here is the complete example of your code by using MYSQLi Object Oriented:
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sql = "SELECT SUM(amount) as amounts FROM transactions WHERE to = 34";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
// output data of each row
while($row = $result->fetch_assoc()) {
echo $row['amounts']. "<br>";
}
}
else
{
echo "0 results";
}
$conn->close();
?>