Database: Bump the recommended version of MySQL to 8.4.

MySQL 8.0 reached end of life on 30 April 2026 but was still the recommended version in `readme.html` and Site Health. MySQL 8.4 is an LTS release supported until April 2032, and has been tested in CI since [59280].

Follow-up to [59280], [62170].

Props lucatume, desrosj, masteradhoc.
Fixes #66637.


git-svn-id: https://develop.svn.wordpress.org/trunk@65399 602fd350-edb4-49c9-b593-d223f7449a82

Author: johnbillion

src/readme.html

@@ -59,7 +59,7 @@ <h2>System Requirements</h2>
 <h3>Recommendations</h3>
 <ul>
 	<li><a href="https://www.php.net/">PHP</a> version <strong>8.3</strong> or greater.</li>
-	<li><a href="https://www.mysql.com/">MySQL</a> version <strong>8.0</strong> or greater OR <a href="https://mariadb.org/">MariaDB</a> version <strong>10.11</strong> or greater.</li>
+	<li><a href="https://www.mysql.com/">MySQL</a> version <strong>8.4</strong> or greater OR <a href="https://mariadb.org/">MariaDB</a> version <strong>10.11</strong> or greater.</li>
 	<li>The <a href="https://httpd.apache.org/docs/2.2/mod/mod_rewrite.html">mod_rewrite</a> Apache module.</li>
 	<li><a href="https://wordpress.org/news/2016/12/moving-toward-ssl/">HTTPS</a> support.</li>
 	<li>A link to <a href="https://wordpress.org/">wordpress.org</a> on your site.</li>

src/wp-admin/includes/class-wp-site-health.php

@@ -17,7 +17,7 @@ class WP_Site_Health {
 	public $is_mariadb                   = false;
 	private $mysql_server_version        = '';
 	private $mysql_required_version      = '5.5';
-	private $mysql_recommended_version   = '8.0';
+	private $mysql_recommended_version   = '8.4';
 	private $mariadb_recommended_version = '10.11';
 
 	public $php_memory_limit;

tests/phpunit/tests/readme.php

@@ -68,16 +68,7 @@ public function test_readme_mysql_version() {
 			}
 		}
 
-		/*
-		 * Per https://www.mysql.com/support/, Oracle actively supports MySQL releases for 5 years from GA release.
-		 *
-		 * The currently recommended MySQL 8.0 branch moved from active support to extended support on 2023-04-19.
-		 * As WordPress core may not be fully compatible with MySQL 8.1 at this time, the "supported" period here
-		 * is increased to 8 years to include extended support.
-		 *
-		 * TODO: Reduce this back to 5 years once MySQL 8.1 compatibility is achieved.
-		 */
-		$mysql_eol    = gmdate( 'Y-m-d', strtotime( $eol_date . ' +8 years' ) );
+		$mysql_eol    = gmdate( 'Y-m-d', strtotime( $eol_date ) );
 		$current_date = gmdate( 'Y-m-d' );
 
 		$this->assertLessThan( $mysql_eol, $current_date, "readme.html's Recommended MySQL version is too old. Remember to update the WordPress.org Requirements page, too." );