select row after update in mysql PDO - php

Question

How to select one row after update in one query with PDO and PHP?
like this:
function giftUpdate($username,$id,$date,$conn){
$update = $conn->prepare("UPDATE gifts SET used = 1 , user = :user , date = :date WHERE id = :id");
$update->bindParam("id" , $id );
$update->bindParam("date" , $date );
$update->bindParam("user" , $username );
$update->execute();
return $update ? true : false;
}
function giftGet($username,$currnetTime,$conn) {
$statment = $conn->prepare("SELECT * FROM gifts WHERE used = 0 ORDER BY `id` ASC");
$statment->execute();
$gift = $statment->fetch(PDO::FETCH_OBJ);
if($gift){
$voucher = $gift->code;
$voucherid = $gift->id;
$vouchertype = $gift->type;
$voucherkey = $gift->keys;
if($voucher){
$giftUpdate = giftUpdate($username,$voucherid,$currnetTime,$conn);
if($giftUpdate){
useUpdate($username , $conn);
}
}
}
usleep(50000);
return $gift ? $gift : false;
}
After update I need select the same row to send it to user.
(i`am one table for vouchers list with 1000row and column 'used' with 0 by default , and with user request i need in one query update this row to be used 1 and select this row.)
my problem in this functions is Some users will receive a duplicate vouchers And a code is assigned to several users.
guys ... for this case Is it possible to use the transaction method? Or do you suggest using a transaction at all?
Edited:
I eventually changed the code below, but I'm still in line :
SELECT id FROM gifts WHERE used = 0 ORDER BY id ASC limit 1 FOR UPDATE)");
But when I put an id from the database instead of this code, it works!
function giftGet($username, $currnetTime, $conn)
{
$uniqid = uniqid('vouchers_');
$update = $conn->prepare("UPDATE gifts SET used = 1, uniqueid =:uniqueid , user = :user , date = :date WHERE id = (
SELECT id FROM gifts WHERE used = 0 ORDER BY `id` ASC limit 1 FOR UPDATE)");
$update->bindParam("date", $currnetTime);
$update->bindParam("uniqueid", $uniqid);
$update->bindParam("user", $username);
$update->execute();
$updaterowCount = $update->rowCount();
if ($updaterowCount)
{
$statment = $conn->prepare("SELECT * FROM gifts WHERE uniqueid = :uniqueid ORDER BY `id` ASC");
$statment->bindParam("uniqueid", $uniqid);
$statment->execute();
$gift = $statment->fetch(PDO::FETCH_OBJ);
$voucherid = $gift->id;
if ($gift)
{
useUpdate($username, $voucherid, $conn);
}
}
return $gift ? $gift : false;
}

Answer 1

I would alter the table gifts and add a column uniqueid(varchar).
then use
$uniqid = uniqid('vouchers_');
and rewrite your update
"UPDATE gifts SET used = 1, uniqueid =:UNIQUEID , user = :user , date = :date WHERE id = (
SELECT id FROM gifts WHERE used = 0 ORDER BY `id` ASC limit 1 FOR UPDATE)";
now you can identify the updated record by uniqueid.
In Your Code there is a time-gap between the select and the update. 2 or more users can start at the same time the select, recieve the same voucher before it is updated with used = 1