PHP-General - About upgrading php

Why must I upgrade or change php script when new version is released ? If I don't upgrade the script, what will happen ?
Thank you

I'm not sure whether you mean upgrading PHP itself or upgrading a PHP script.

If a new version of a PHP script that you're using is released, you generally should update. Software updates in generally often contain security fixes, so the result of not updating could mean your site gets hacked.

If a new version of PHP is released, upgrading is less important; but like all software PHP updates include security fixes too. Additionally, newer PHP scripts will not work with older versions of PHP, so upgrading is important because it allows you to continue upgrading your PHP scripts.

@E-Oreo : I mean upgrading PHP Script. Not PHP itself. Because i always update php script runner (PHP itself) . thank u ^_^

it depends.. you need to see what has changed (functions usually which you will be using in your script), removed from your version to the new version. If nothing has changed, you dont need to do anything.

for example: for php 4 and 5, this will work: if (isset($_POST['varoiable'])) {

so no need to change the script.

you could always run your script in the new version and see if everything is running smoothly

hey all thanks for your answers.

i know upgrading php script is important for security

if i have enough money, i will use ssl also for my site