WordPress has a health check for your site. You can see a summary of the results of the check on your dashboard. This is the results of mine since updating to WordPress 5.9:
It’s good, to paraphrase the late Roy Walker , but it’s not right: there’s one item that needs my attention. Clicking the
Site Health screen link takes me to, surprisingly enough, the Site Health screen, which you can go to directly at http(s)://example.com/wp-admin/site-health.php.
My health screen shows me that
One or more recommended modules are missing, specifically that:
The optional module, intl, is not installed, or has been disabled.
This is an internationalisation module , apparently.
I went to my trusty command line, and attempted to use apt install intl to install this missing module. However, I was thwarted:
sudo apt install intlReading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package intl
It seemed I had the name of the package wrong, despite using the name given in the list of optional PHP modules recommended by WordPress . I rummaged around the internet and found an indication of how to install it from the comments on the PHP page for installing the intl package : the module name must be prefixed with PHP and its version number:
sudo apt install php7.4-intlReading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: php7.4-intl 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 126 kB of archives. After this operation, 528 kB of additional disk space will be used. Get:1 http://ppa.launchpad.net/ondrej/php/ubuntu focal/main amd64 php7.4-intl amd64 7.4.27-1+ubuntu20.04.1+deb.sury.org+1 [126 kB] Fetched 126 kB in 0s (5,992 kB/s) Selecting previously unselected package php7.4-intl. (Reading database ... 158803 files and directories currently installed.) Preparing to unpack .../php7.4-intl_7.4.27-1+ubuntu20.04.1+deb.sury.org+1_amd64.deb ... Unpacking php7.4-intl (7.4.27-1+ubuntu20.04.1+deb.sury.org+1) ... Setting up php7.4-intl (7.4.27-1+ubuntu20.04.1+deb.sury.org+1) ... Creating config file /etc/php/7.4/mods-available/intl.ini with new version Processing triggers for libapache2-mod-php7.4 (7.4.27-1+ubuntu20.04.1+deb.sury.org+1) ... Processing triggers for php7.4-cli (7.4.27-1+ubuntu20.04.1+deb.sury.org+1) ...
I expected it to work after that, but I got the same error. I looked in phpinfo.php , and it wasn’t there either, although it was listed as being installed .
One of the comments on  said that I should uncomment out the intl package (by deleting the semi-colon
;) on the appropiate line of php.ini then restart the Apache server:
I found the file  and followed the instructions, adapting them for Ubuntu rather than Windows, and reloading Apache, rather than restarting it :
sudo nano /etc/php/7.4/apache2/php.ini
[…] ;extension=gmp extension=intl ;extension=imap […]
sudo service apache2 reload
Then I looked in phpinfo.php again; lo and behold, there it was:
This seemed promising; I looked back at the Site Health screen: the error had gone, and WordPress was very happy about it: