How to do + or - in php? - php

Question

I want to have a form in following way:
[-] [value] [+]
I don't know how to script the logic to get the value 1 higher or 1 lower in PHP.
I assumed something like following would work:
<?php
$i = 0;
if($_SERVER['REQUEST_METHOD'] == 'POST')
{
if(isset($_POST['plus']))
{
$i++;
}
if(isset($_POST['min']))
{
$i--;
}
}
?>
and my form is as following:
<form action="" method="post">
<input type="submit" name="min" value="-"> <input type="text" value=<?php echo $i ?> > <input type="submit" name="plus" value="+">
</form>
But I'm only getting either a 1 or a -1. Can someone show me how to do this in a good way?

Answer 1

Try this:
<?php
if($_SERVER['REQUEST_METHOD'] == 'POST')
{
$i = $_POST['current_value'] || 1;
if(isset($_POST['plus']))
{
$i++;
}
if(isset($_POST['min']))
{
$i--;
}
}
?>
and this:
<form action="" method="post">
<input type="submit" name="min" value="-"> <input name="current_value" type="text" value=<?php echo $i ?> > <input type="submit" name="plus" value="+">
</form>
You need some way to get the current value to persist between requests - depending on your use case, you may need database storage as Rocket mentions, or this simple passing back of the current value may be enough.

Answer 2

PHP will simply load code on the server-side and run when the page is loaded. If you are looking to dynamically increment/decrement the value while remaining on the same page, I suggest you look into learning Javascript and jQuery.
Reference: https://developer.mozilla.org/en/JavaScript/
Reference: http://jQuery.com/

Answer 3

What is happening with your code is that you are incrementing a global variable that you set to 0 in the beginning. That is why the only values you get back or 1 or -1. This can be fixed by passing the variable you increment each time instead of using a global variable. That way it keeps the value between each plus and minus and doesn't keep resetting it.