Is my WordPress plugin compatible with PHP 8.3, 8.4 or 8.5?

What the labels say, and what they do not

A plugin’s listing carries two fields that look like answers and are not.

A changelog line such as “PHP 8.4 compatibility” is the author’s statement about the release it appears in. It helps, and it cannot cover PHP versions released after it was written. Treat every label as a hint, and test.

Three ways to find out

Test on a staging copy

Switch a copy of your site to the PHP version you want, add these lines to wp-config.php, click through the site and read wp-content/debug.log.

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );

Good at: it runs the real code with your real settings and data. Limits: only the code you trigger runs. A task that runs once a month, an export or a rarely used admin screen can be missed.

Read the changelog and the support forum

Good at: it is quick, and it shows whether the author has dealt with newer PHP versions and whether other users hit problems on yours. Limits: it depends on the author writing things down, an empty forum is not evidence that all is well, and a note describes the release it was written for, not the one you run.

Run a static scan

A static scan reads the code without running it and matches it against lists of constructs that PHP removed or deprecated. It can be a plugin, like the one in the box further down, or a command-line tool such as PHP_CodeSniffer with the PHPCompatibility rules.

Good at: it covers every file, including code that rarely runs, scanning does not execute the plugin’s code, and it names a file and a line. Limits: it only finds constructs it has rules for, it cannot see problems that depend on your data or server setup, and a flagged line may sit in code that never runs.

Use two of the three: a scan finds known problem constructs everywhere, and a staging test shows what happens on your site.

Ten changes to look for

All ten are deprecations. The code still runs and PHP logs a notice, but a deprecated feature may be removed in a later PHP version. Each notice ends with the file and line, for example in /path/to/plugin.php on line 12, which is how a log or a scan points you to the spot. The notices below are the text PHP prints. We ran every before and after pair on PHP 8.3.36, 8.4.27 and 8.5.12.

$name = get_class();

$name = self::class;

function render( string $title = null ) {
	return $title;
}

function render( ?string $title = null ) {
	return $title;
}

error_reporting( E_ALL & ~E_STRICT );

error_reporting( E_ALL );

trigger_error( 'Cannot connect', E_USER_ERROR );

throw new RuntimeException( 'Cannot connect' );

fputcsv( $handle, $row );

fputcsv( $handle, $row, ',', '"', '\\' );

curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true );
curl_setopt( $ch, CURLOPT_BINARYTRANSFER, true );

curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true );

$response = curl_exec( $ch );
curl_close( $ch );

$response = curl_exec( $ch );

$user = `whoami`;

$user = shell_exec( 'whoami' );

$count = (integer) $value;

$count = (int) $value;

$options = [ PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true ];

$buffered = defined( 'Pdo\Mysql::ATTR_USE_BUFFERED_QUERY' )
	? Pdo\Mysql::ATTR_USE_BUFFERED_QUERY
	: PDO::MYSQL_ATTR_USE_BUFFERED_QUERY;
$options = [ $buffered => true ];

Beyond these ten

Removals are harsher: a removed function ends in a fatal error, not a notice. One example is PHP 8.4 moving the IMAP, OCI8, PDO_OCI and PSpell extensions out of the PHP distribution (PHP manual). The manual lists every release’s backward-incompatible changes and deprecations; the links are under Sources.

Sources

• PHP manual, deprecated features: 8.3, 8.4, 8.5.
• PHP manual, backward-incompatible changes: 8.3, 8.4, 8.5.
• PHP manual, removed extensions in 8.4.
• The notices and the before and after code were run on PHP 8.3.36, 8.4.27 and 8.5.12 on 1 November 2026.

General information, not a guarantee for any particular plugin or site. Test on a copy before you change your live site. This page was last checked on 1 November 2026.