WordPress requires json, hash and mysqli. Recommended modules add image processing, remote requests, archive handling and other capabilities. A hosting panel’s full list includes options your site may never use.
The tables below separate core requirements from recommendations and feature-specific choices. They follow the WordPress Hosting Handbook, checked on 2 October 2026. The host screenshot is an example of the interface, not a tested configuration for every WordPress site.
Required and built-in PHP extensions
| Extension | Category | Purpose | What to check |
|---|---|---|---|
json | Required | JSON data | Built into PHP 8.0+; no optional checkbox needed |
hash | Required | Hashing | Built into PHP 7.4+ |
mysqli | Required | WordPress database connection | Must load in the website’s PHP runtime |
pcre | Built-in | Regular expressions | Normally no hosting action |
mysqlnd | Driver | Supports database extensions | Does not replace mysqli |
PHP’s manuals confirm the built-in status of JSON and hash. The MySQL native driver documentation explains the driver layer.
A host may label its MySQLi package nd_mysqli. Confirm that it provides mysqli; do not select conflicting packages just because their names look related. pdo_mysql is a separate database API. Enable it when a plugin or custom application needs it, not as a replacement for WordPress’s mysqli connection.
Recommended modules to review with your host
| Module | Purpose | Configuration note |
|---|---|---|
curl | Remote requests | Check outbound connections |
dom, xml | XML/document processing | Host packages may group these |
exif, fileinfo | Image metadata and file types | Check uploads |
imagick | Image processing | Needs ImageMagick |
intl, mbstring | International text | Check multilingual features |
openssl | Encrypted outbound connections | Distinct from the site’s HTTPS certificate |
zip | Archive handling | Check updates and exports |
igbinary | Serialization | Confirm support in the consuming cache/application |
Treat this as a review list. A module can already be enabled without appearing as a selectable option. Ask the host to verify availability for the exact domain and PHP version, then test the feature that depends on it.
Optional, fallback and plugin-specific choices
| Module | Category | When to consider it |
|---|---|---|
gd | Image fallback | Image handling when Imagick is unavailable |
opcache | Bytecode cache | Host-managed caching of compiled PHP |
redis, memcached, apcu | Object caching | Only with a matching cache setup |
simplexml, xmlreader, sodium, zlib | Feature/fallback | Match application dependencies |
pdo_mysql, soap, bcmath, imap | Plugin-specific | Only when a component requires them |
Check the relevant module and plugin documentation before enabling optional dependencies. For example, OPcache caches compiled PHP code, while a Redis client connects code to Redis. An extension checkbox alone does not configure persistent object caching in WordPress.
Avoid enabling every extension as a precaution. Keep a record of why each optional module is present, so the same feature can be checked when changing PHP branches.
Which PHP version should these modules run on?
Use the recommended PHP version guide to choose a branch. For WordPress 6.9 or later, PHP 8.5 is a candidate after the host, plugins, theme, extensions and critical flows pass staging. PHP 8.4 is another supported option when a dependency blocks 8.5.
PHP 8.4 receives active support until 31 December 2026 and security fixes until 31 December 2028, according to php.net.
Recheck extensions whenever you change branches: a host can enable different modules for each version. PHP 8.2 reaches end of life on 31 December 2026; follow the PHP 8.2 upgrade plan if it is still your production version.
Example: a hosting panel’s PHP 8.5 selector
Host interface example, not a universal checklist. The selected optional modules reflect that environment. Use the tables above and your plugin requirements to decide what your site needs. A built-in module may have no checkbox, and your host may use different names.
Check and enable modules for the correct runtime
- In WordPress, open Tools → Site Health. Read the Status warnings, then use Info → Server to confirm the web PHP version. Site Health checks important modules but is not an inventory of every dependency a plugin can have.
- In the hosting panel, select the exact domain. Confirm its PHP version and handler before changing modules.
- If your host provides Select PHP Version, open its extension settings and enable the needed module. This selector is not present on every cPanel account. Other hosts install modules through managed packages or support requests.
- Apply the host’s required reload or restart procedure. On managed hosting, ask support to do this.
- Recheck Site Health and exercise the affected operation, such as uploading an image, installing an update or submitting a form.
If you have shell access, php -v, php -m and php --ini report the command-line version, modules and configuration. They do not prove that PHP-FPM or another web handler uses the same configuration. Ask the host to compare them when a CLI job succeeds but the website fails.
Avoid leaving a public phpinfo() page online. It exposes server configuration. Prefer the host’s authenticated diagnostics; remove any temporary diagnostic file after use.
Fix missing JSON, MySQLi and other extension errors
Read the exact message first. Similar symptoms can come from different layers.
The exact messages WordPress shows
WordPress core checks for its required extensions itself. These are the messages it prints, quoted from the current WordPress source code (checked 17 October 2026). The version number changes with your WordPress release.
“WordPress 7.0 requires the json PHP extension.”
The site stops before it loads, from the requirements check in wp-includes/load.php. WordPress lists json and hash as required in wp-includes/version.php. JSON is always enabled on PHP 8.0 and later, and hash on PHP 7.4 and later, so this message means the domain still runs PHP 7.x. The quick repair is to tick json for PHP 7.4 in the host’s PHP extensions panel. The better fix is to move the domain to PHP 8.3 or later, where the message cannot appear.
“The update cannot be installed because WordPress 7.1 requires the json PHP extension.”
The same check runs in the updater, wp-admin/includes/update-core.php, before any file is replaced. The site keeps running its current version and simply cannot update. The fix is the same: enable json on PHP 7.4 or, better, move to PHP 8.3 or later, then run the update again.
“Your PHP installation appears to be missing the MySQL extension which is required by WordPress.”
This also comes from wp-includes/load.php. WordPress shows it when the mysqli functions are missing and no database drop-in is installed, and adds “Please check that the mysqli PHP extension is installed and enabled.” Enable the host’s MySQLi package for that domain and PHP version; mysqlnd alone does not provide it.
Other symptoms and where to look:
| Message or symptom | What to verify | Next action |
|---|---|---|
Missing json, or undefined json_encode() | Actual web runtime and the component reporting the error | JSON is built in on PHP 8; ask the host to investigate a runtime mismatch or inaccurate diagnostic |
Missing MySQL extension, or undefined mysqli_connect() | mysqli availability for this domain | Enable the host’s matching MySQLi package; mysqlnd alone is insufficient |
| Error establishing a database connection | Credentials, database service, permissions and network access | Diagnose the database connection; this message alone does not identify a missing module |
Undefined curl_init() or ZipArchive missing | curl or zip in the web handler | Ask the host to enable the named module for this PHP version |
| “The response is not a valid JSON response” in the editor | REST request status and response body | Check redirects, authentication, server errors and security rules before blaming PHP’s JSON module |
For a reported JSON problem:
- Note where it appears: Site Health, the editor, a plugin or the server log. Record the failing action and time.
- Confirm the PHP version serving that domain. On PHP 8+, searching for a JSON checkbox is not a fix because the extension is always enabled.
- If an editor request fails, inspect that request in the browser Network panel. An HTML login page, error page or warning printed before the JSON is a response problem, even when PHP supports JSON correctly.
- On staging, review the PHP error log and isolate the plugin, theme or server rule involved. Keep debug output out of public responses.
- Give the host the domain, web PHP version, handler and error timestamp. Repeat the failed action after the repair.
After enabling a module, verify the feature rather than stopping at a green checkbox. For stores, include sandbox checkout, payment callbacks, order emails and scheduled tasks. For page builders, use the Elementor requirements and test plan.
If a missing module or legacy plugin blocks an upgrade, our WordPress support service can assess the configuration and agree a scoped repair.
Frequently asked questions
What is a PHP extension?
A PHP extension is a compiled module that adds functions to PHP, such as mysqli for MySQL databases, curl for HTTP requests or imagick for image processing. Hosts often enable extensions separately for each PHP version, so switching versions can drop one WordPress needs.
Which PHP extensions are required for WordPress?
The WordPress Hosting Handbook lists json, hash and mysqli as required. JSON is always available in PHP 8.0 and later; hash is always available from PHP 7.4. mysqli must be available to the PHP runtime serving WordPress. mysqlnd is a database driver, not a replacement for mysqli.
Why is there no JSON checkbox in my PHP settings?
JSON is built into PHP 8.0 and later and cannot be disabled. Its absence from the hosting panel's optional extension list does not mean JSON support is missing. Check the PHP runtime serving the affected domain if a diagnostic still reports a problem.
Is mysqlnd enough for WordPress?
No. WordPress uses mysqli to connect to its database. mysqlnd can be the underlying driver, but does not replace that extension. Some hosts use labels such as nd_mysqli; ask the host which package provides mysqli for the site's PHP handler.
Which PHP extensions are recommended for WordPress?
Recommended modules include curl, dom, exif, fileinfo, imagick, intl, mbstring, openssl, xml and zip. The Hosting Handbook also recommends igbinary for serialization. Match the enabled modules to your host, plugins and actual features rather than copying every checkbox from a screenshot.
Should I enable Redis and Memcached?
Enable the client needed by your configured object cache. Installing an extension alone does not set up a cache service or connect WordPress to it. OPcache has a different role: caching compiled PHP code.
How do I check and enable PHP extensions?
Use WordPress Site Health and the hosting panel for the affected domain. If your host provides Select PHP Version, check the active version and its Extensions tab. Other hosts manage modules themselves. Recheck the website after a change because command-line PHP can use a different configuration.
Does WooCommerce need a different extension list?
Start with WordPress requirements, then check the requirements of WooCommerce and each payment, shipping, import and subscription extension you use. A plugin may add dependencies that are not WordPress core requirements. Test checkout and scheduled work on staging.
