PHP 8.1 to 8.3: the shortest way off an unsupported branch

Your software stops at 8.3

Some platform releases list 8.3 as their highest PHP version, Laravel 10 and Magento 2.4.7 among them. Then the platform has made the decision for you.

Less to change

Two releases instead of three, and no 8.4 extension removals. When the 8.1 server is exposed, a smaller change set reaches production sooner.

Enough runway to plan properly

8.3 gets security fixes until 31 December 2027: time to upgrade the application itself, then move PHP again without the pressure you are under now.

The next hop is already mapped

Clearing 8.4's deprecations while you are on 8.3 makes the following move a small one. The list is further down this page.

If none of these applies and your platform supports it, the 8.1 to 8.4 route gives a year more support for one more release of changes.

First release: 8.2

PHP 8.2: what changed, and where it hides in 8.1 code

Most 8.2 changes surface as deprecation notices rather than errors. One trigger that turns up in older code looks like this:

<?php
class Customer
{
    public int $id;
    public string $email;

    public function __construct(array $row)
    {
        foreach ($row as $key => $value) {
            // PHP 8.2 and later: deprecated for any key not declared above
            $this->$key = $value;
        }
    }
}

Sources on php.net: 8.2 incompatible changes, 8.2 deprecations, 8.2 other changes.

Before the next step

Clear these on 8.3, and the move to 8.4 shrinks

8.3's support ends on 31 December 2027, so another PHP move is already on the calendar. Each of these 8.4 changes can be fixed in code that still runs on 8.3.

• Nullable types spelled out. 8.4 deprecates a parameter that only accepts null because its default is null. Adding the ?, as in ?Logger $logger = null, is valid on 8.1 and 8.3 too.
• Fatal user errors. trigger_error($message, E_USER_ERROR) is deprecated in 8.4; throw an exception instead.
• CSV escape characters. Leaving out the $escape argument of fgetcsv(), fputcsv() and str_getcsv() is deprecated; pass it explicitly now.
• mysqli housekeeping calls. mysqli_ping(), mysqli_kill() and mysqli_refresh() are deprecated in 8.4.
• Extensions leaving PHP. From 8.4, IMAP, OCI8, PDO_OCI and PSpell are distributed through PECL only. If you use any of them, start on the replacement while 8.3 still bundles them.

php.net: migrating from PHP 8.3 to 8.4

Testing and rollout

Testing the move, and switching over

1. Staging on 8.3.36 or later, with the production web server, PHP handler and a recent copy of the database.
2. Extensions matched, comparing php -m with a phpinfo() page served by the web server, since the CLI may read another php.ini (php --ini shows which).
3. Composer resolved against 8.3: config.platform.php set to 8.3.36, composer update, a committed lock file, then composer check-platform-reqs on staging to confirm the real runtime matches.
4. Full logging: error_reporting = E_ALL, log_errors = On, display_errors = Off. The shipped php.ini-production drops deprecations, which is fine for live but hides the 8.2 and 8.3 notices you need to see here.
5. Every route through the site tested: sign-in, search, forms, payments, emails, file uploads, cron and queue workers.
6. A planned cutover, at a quiet time, with 8.1 left installed but unused and the error log under watch afterwards.