Можно так:
<?php
require_once 'vendor/connect.php';
$login = mysqli_real_escape_string($connect, $_SESSION["login"]);
$query = mysqli_query($connect, "SELECT * FROM `users` WHERE login = '$login'");
$balance = mysqli_fetch_assoc($query);
echo 'Balance:' . $balance['balance']. PHP_EOL;
if(isset($_POST['click'])) {
mysqli_query($connect, "UPDATE `users` SET `balance`=`balance`+0.001 WHERE login = '$login'");
echo 'New balance:' . ($balance['balance'] + 0.001) . PHP_EOL;
}
?>
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А лучше так:
<?php
require_once 'vendor/connect.php';
/* prepare statement */
$stmt = $connect->prepare("SELECT `balance` FROM `users` WHERE login = ? ");
/* bind parameters for login */
$stmt->bind_param("s", $_SESSION["login"]);
/* execute query */
$stmt->execute();
$stmt->bind_result($balance);
/* fetch value */
$stmt->fetch();
/* free result to next use */
$stmt->free_result();
echo 'Balance:' . $balance . PHP_EOL;
if (isset($_POST['click'])) {
/* prepare statement */
$stmt = $connect->prepare("UPDATE `users` SET `balance`=`balance`+0.001 WHERE login = ? ");
/* bind parameters for login */
$stmt->bind_param("s", $_SESSION["login"]);
/* execute query */
$stmt->execute();
echo 'New balance:' . ($balance['balance'] + 0.001) . PHP_EOL;
}
?>
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