Ticket #21663: 21663.13.diff

src/wp-includes/wp-db.php

@@ -569 +569 @@
                         $this->show_errors();
 
                 /* Use ext/mysqli if it exists and:
+                 *  - USE_EXT_MYSQL is defined as false, or
                  *  - We are a development version of WordPress, or
                  *  - We are running PHP 5.5 or greater, or
                  *  - ext/mysql is not loaded.
                  */
                 if ( function_exists( 'mysqli_connect' ) ) {
-                        if ( version_compare( phpversion(), '5.5', '>=' ) || ! function_exists( 'mysql_connect' ) ) {
+                        if ( defined( 'USE_EXT_MYSQL' ) ) {
+                                $this->use_mysqli = (bool) USE_EXT_MYSQL;
+                        } elseif ( version_compare( phpversion(), '5.5', '>=' ) || ! function_exists( 'mysql_connect' ) ) {
                                 $this->use_mysqli = true;
                         } elseif ( false !== strpos( $GLOBALS['wp_version'], '-' ) ) {
                                 $this->use_mysqli = true;
-                        }
                 }
 
                 $this->init_charset();