Values not updating or saving when button is clicked in PHP? - php

Question

Status:
Apprentice.
My PHP knowledge:
Beginner level.
What I am trying to achieve with my PHP code:
Update the health bar input when ever the user clicks on the submit button.
<form>
<input type="submit" value="Attack">
</form>
So if the condition is true and the post has been done then I want to subtract 25 from the variable health which is then equal to another variable named input.
The problem:
I cant figure out why the health is not updating and how to save the updated value even if the user refreshes and then substracting 25 with the updated health everytime the user clicks on "attack".
What I tried:
Apart from doing some PHP research about Session_start() im not sure how to use it in this context. Im not even entirely sure why my conditional is faulty. I get no error messages what so ever but when I remove my if statement and echo the my bar variable then it doesnt work either as I dont get any number at all, which of course makes me suspect that my math is not working.
<?php
$health = 100;
$input = "";
$bar = '<div>' . $health . $input . '%' . '</div>' . '<div>' . 'Stamina' . '</div>';
echo $bar;
if (isset($_POST['submit'])) {
$health - 25 == $input;
echo $bar;
}
?>
Question:
Why does'nt my value of health / input update? How can I save the session and substract from the new variable the next time an attack is made?

Answer 1

Your PHP is stateless so it has no record of what health was - it's simply reset to 100 every time.
You need to either use sessions, or simply pass back in the value of health each time:
<?php
$health = (isset($_REQUEST['health']) ? (int) $_REQUEST['health'] : 100);
if (isset($_REQUEST['submit'])) {
$health = $health - 25;
}
$input = "";
$bar = '<div>' . $health . $input . '%' . '</div>' . '<div>' . 'Stamina' . '</div>';
echo $bar;
?>
<form action="attack.php" method="post">
<input type="submit" name="submit" value="Attack">
<input type="hidden" name="health" value="<?php echo $health; ?>">
</form>
A couple of other points:
1) I'm not sure what the significance of $input is
2) You should really include a method in your form tag of either get or post - in the PHP I've used I have referenced $_REQUEST which features the values of both $_GET and $_POST
3) Notice I cast the value of $_REQUEST['health'] to an integer because this is output in the hidden HTML field and this helps to avoid XSS exploits.
If you want the health variable to carry over on to other pages or scripts then you might prefer to use a session. Revised code as follows:
<?php
session_start();
$health = (isset($_SESSION['health']) ? $_SESSION['health'] : 100);
if (isset($_REQUEST['submit'])) {
$health = $health - 25;
$_SESSION['health'] = $health;
}
$input = "";
$bar = '<div>' . $health . $input . '%' . '</div>' . '<div>' . 'Stamina' . '</div>';
echo $bar;
?>
<form action="attack.php" method="post">
<input type="submit" name="submit" value="Attack">
</form>
One final comment is that using the session method a user cannot tamper with their own health score. Whereas using the hidden input method the user could potentially change the value of the field and tamper with their health score if they had the technical know-how.

Answer 2

change the form to the form below -
<form action='' method='POST'>
<input type="submit" name='submit1' value="Attack">
</form>
Then you can do -
if (isset($_POST['submit1']))
{
echo "button was pressed";
/// do other stuff.....
}

Answer 3

Define your form like:
<form method="POST">
That might do the trick. And you might need an hidden input field for the current health.

Answer 4

Firstly, forms default to a GET method if omitted.
Therefore, you need to specify it in your form tag
method="post"
Then your conditional statement will fail, since the submit input doesn't have the name attribute.
Add name="submit" to it.
Then this $health - 25 == $input; that doesn't make any sense and I don't know what you're trying to do here.
As stated in another answer by Mr Carrot, you'd want to use $health = $health - 25;
I'll let you look through the answers given, but this gives you a good indication as to what's going on.
Using error reporting would have signaled notices.
Add error reporting to the top of your file(s) which will help find errors.
<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
// rest of your code
Sidenote: Displaying errors should only be done in staging, and never production.