WordPress and PHP 8.2: what changes for plugins and themes

Is WordPress ready for PHP 8.2?

PHP 8.2 was released on 8 December 2022. Its active support ended on 31 December 2024; it gets security fixes until 31 December 2026 (php.net).

The WordPress core team’s compatibility page lists WordPress 6.1 and later as compatible with PHP 8.2. That covers WordPress itself; the changes below concern the code of your plugins and theme.

Already running PHP 8.2? Then the more urgent question is the next version: what the end of security fixes means and which version to choose is in PHP 8.2 reaches end of life.

The short version

The PHP 8.2 changes you’re most likely to meet in plugins and themes. php.net lists the full set of deprecated features and backward incompatible changes.

None of these stops a page. If your site comes from PHP 7.4, the bigger step is the one to PHP 8.0, which removed functions and syntax outright: see moving from PHP 7.4 to PHP 8.

Dynamic properties

The PHP 8.2 notice you’ll see most in WordPress logs. php.net: “The creation of dynamic properties is deprecated, unless the class opts in by using the #[\AllowDynamicProperties] attribute.” (php.net) What it means, why it isn’t urgent and who fixes it has its own guide: “Creation of dynamic property … is deprecated”.

"${var}" in text

Older code sometimes puts variables into text as "${name}". PHP 8.2 still runs it and adds a notice:

<?php
$name = 'Anna';
echo "Hello ${name}!\n";

Hello Anna!

Deprecated: Using ${var} in strings is deprecated, use {$var} instead in /var/www/html/wp-content/plugins/simple-greeting/simple-greeting.php on line 3
Hello Anna!

php.net: “The “${var}” and “${expr}” style of string interpolation is deprecated.” (php.net) The fix is a two-character change for whoever maintains the code; both wordings of the notice and the fixes are in “Using ${var} in strings is deprecated”.

utf8_encode() and utf8_decode()

Import and export plugins use these to convert between UTF-8 and the older ISO-8859-1 character set. PHP 8.2 marks both: “utf8_encode() and utf8_decode() have been deprecated.” (php.net)

<?php
$latin1 = "Caf\xE9";               // "Café" in ISO-8859-1, as an old CSV export stores it
echo utf8_encode($latin1), "\n";

Café

Deprecated: Function utf8_encode() is deprecated in /var/www/html/wp-content/plugins/old-importer/import.php on line 3
Café

The replacement, and a case where the old function quietly produced wrong characters, are in “utf8_encode() is deprecated”.

Callbacks written as "self::method"

A plugin can pass one of its own methods as a callback in several ways. PHP 8.2 deprecates the ones that start with self, parent or static as text. php.net: “Callables that are not accepted by the $callable() syntax (but are accepted by call_user_func()) are deprecated.” (php.net)

<?php
class Price_List {
    public static function format($price) {
        return number_format($price, 2);
    }

    public static function all(array $prices) {
        return array_map('self::format', $prices);
    }
}

echo implode(', ', Price_List::all([5, 12.5])), "\n";

5.00, 12.50

Deprecated: Use of "self" in callables is deprecated in /var/www/html/wp-content/plugins/price-list/price-list.php on line 8
5.00, 12.50

Encodings in mbstring functions

mb_convert_encoding() with HTML-ENTITIES was a shortcut for turning accented letters into HTML codes. php.net: “Usage of the QPrint, Base64, Uuencode, and HTML-ENTITIES ’text encodings’ is deprecated for all MBString functions.” (php.net)

<?php
echo mb_convert_encoding('Café', 'HTML-ENTITIES', 'UTF-8'), "\n";

Café

Deprecated: mb_convert_encoding(): Handling HTML entities via mbstring is deprecated; use htmlspecialchars, htmlentities, or mb_encode_numericentity/mb_decode_numericentity instead in /var/www/html/wp-content/plugins/old-importer/import.php on line 2
Café

PHP’s own notice names the replacements, so whoever fixes it knows where to start.

What changes silently

Some PHP 8.2 changes give no message at all. The one most likely to matter in a WordPress site, from php.net: “strtolower(), strtoupper(), stristr(), stripos(), strripos(), lcfirst(), ucfirst(), ucwords(), and str_ireplace() are no longer locale-sensitive.” (php.net) On a server set to a language with special letters, these functions used to change their case; from PHP 8.2 they only change A to Z. php.net: “Localized versions of these functions are available in the MBString extension.” (php.net)

No code check can tell whether a plugin relied on the old behaviour; a quick look at text with accented capital letters after the switch does.

How to check your site before switching