Best way to update a single column in MySQL table? - php

Question

So im fairly new to coding, and have just started on a project for fun.
I try to build a RPG game, and i have got to the point where players can fight and take damage. So i want to add a passive health regeneration.
So i was thinking that i would use a conjob to request a php file every 10min and update all players HP with +10.
What i have got with my very poor MySQL knowlege is;
<?php
/*
* hp_reg.php, auto updater +10hp to players.
*/
//DATABAS CONNECTION
$dbserver="my";
$dbusername ="db";
$dbpassword ="conection";
$db ="information";
//CREATE CONNECTION
$conn = new mysqli($dbserver, $dbusername, $dbpassword, $db);
$query = "SELECT health FROM users";
$result = mysqli_query($conn, $query);
$row = mysqli_fetch_assoc($query);
$newhp = $result + 10;
$sql = "INSERT INTO users(health) VALUES ($newhp)";
Wich clearly will not work at all!
Any tips on what to change in order to get it to work?
All pointers are much appreciated.

Answer 1

$sql = "UPDATE users SET health = health + 10";
Updated Code
<?php
/*
* hp_reg.php, auto updater +10hp to players.
*/
//DATABAS CONNECTION
$dbserver="my";
$dbusername ="db";
$dbpassword ="conection";
$db ="information";
//CREATE CONNECTION
$conn = new mysqli($dbserver, $dbusername, $dbpassword, $db);
$sql = "UPDATE users SET health = health + 10";
$result = mysqli_query($conn, $sql);

Answer 2

To increase the health column of all users by 10, you can execute the following query:
UPDATE users SET health = health + 10

Answer 3

Assuming:
you want update health of One user;
each user have an unique id;
the unique id is stored in your database as userID (if not, change it with your correct field name);
you have to try in this way:
$query = "SELECT health FROM users WHERE userID='$userID'";
$result = mysqli_query( $conn, $query );
$row = mysqli_fetch_assoc( $query );
$newhp = $row['health'] + 10;
$query = "UPDATE users SET health='$newhp' WHERE userID='$userID'";
$result = mysqli_query( $conn, $query );
At last, take a look to how preventSQL-injection in PHP and how check if your result is empty