PHP 8.3 compatibility checker for WordPress: check before you leave PHP 8.2

Why PHP 8.3, and why now

PHP 8.2 gets security fixes until 31 December 2026; PHP 8.3 until 31 December 2027 (php.net). wordpress.org says: “To run WordPress, it’s recommended your host supports: PHP version 8.3 or greater.” (wordpress.org) So 8.3 is the first candidate for a site leaving 8.2 (PHP 8.2’s end of life).

What a PHP 8.3 checker must find

CompatNav runs 4 checks for PHP 8.3, each one a change from php.net’s list of PHP 8.3 deprecations:

None of them stops a page. A typical one, in a class that asks for its own name the old way:

<?php
class Invoice {
    public function describe(): string {
        return 'Created by ' . get_class();
    }
}

echo (new Invoice())->describe(), "\n";

Created by Invoice

Deprecated: Calling get_class() without arguments is deprecated in /var/www/html/example.php on line 4
Created by Invoice

The fix is in “Calling get_class() without arguments is deprecated”, and every PHP 8.3 change in plain words in WordPress and PHP 8.3.

What only your error log shows

Three PHP 8.3 changes depend on the data a site handles, so no check that reads code can tell whether they will happen:

• DateTime::modify() with a date it can’t read now throws an exception, which stops the page unless the plugin catches it. Before, it gave a warning and returned false.
• A list that starts at a negative index continues from it, instead of jumping to 0.
• ++ on an empty or non-alphanumeric string adds a deprecation notice.

All three are explained, with tested examples, in WordPress and PHP 8.3. After switching, keep the error log on for a week (the WordPress debug log).

Coming from an older version

The check must cover every version between yours and 8.3, because each brought its own changes. CompatNav compares the PHP version your site runs today with the one you choose and reports only what changes between the two:

Whatever the version, it also reports a file that PHP 8.3 can no longer read at all. The PHP 8.0 and 8.1 changes that stop code are in moving from PHP 7.4 to PHP 8 and WordPress and PHP 8.1.

Run the check

The check runs on your own server and only reads files; no code, file names or results are sent anywhere. Getting started shows each screen.