Add Numbers Together From Mysql Database in PHP

Question

I need to add some numbers together that are being pulled from a MySQL table to get a total value.

Currently the issue I have is the numbers being added to the end of a string instead.

e.g:

1,2,3,4 becomes 1234 instead of 10

Here is what I am using to get the numbers from the database:

$count = mysqli_query($connect, "SELECT QUANTITY FROM Table");

while($row = mysqli_fetch_assoc($count)) {
    $total .= $row['Quantity'];
    //I Have also tried
    $total .= (int)$row['Quantity'];
}

echo $total;

The Quantity Column is set to be an INT in the table so I would have expected it to add together automatically. What am I doing wrong?

Why not do SELECT SUM(QUANTITY) AS QUANTITY FROM Table as your database query? — Mark Baker
– Mark Baker, Commented Feb 8, 2018 at 12:18
@FunkFortyNiner I tried that and it gave the error Undefined Variable $total. I've now realised I should have created the variable initially as 0. So it works, thanks. — Edward144
– Edward144, Commented Feb 8, 2018 at 12:21
you could have first assigned it as $total = ""; then the rest with the plus sign ;-) that is but one way to do it. That's why you got the undefined notice. — Funk Forty Niner
– Funk Forty Niner, Commented Feb 8, 2018 at 12:21

Twinfriends · Accepted Answer · 2018-02-08 12:21:44Z

4

You should probably look at the difference between .= and +=

By adding a . in front of = you concatenate - You add the value ad the end of the variable.

If you would use a + in front of your = you would actually get the result you want.

$count = mysqli_query($connect, "SELECT QUANTITY FROM Table");
$total = 0;
while($row = mysqli_fetch_assoc($count)) {
    $total += $row['Quantity'];
}
echo $total;

http://php.net/manual/en/language.operators.string.php

answered Feb 8, 2018 at 12:21

Twinfriends

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