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If we were not using pantheon wordpress_network upstream and the default wp-config.php that comes with it, or if we were setting up the multisite from scratch, we would have added the following to the bottom of wp-config-local.php(since the wp-config-ddv.php file is auto-generated by DDEV and we have less control over it):

define('WP_ALLOW_MULTISITE', true);
define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', false);
define('DOMAIN_CURRENT_SITE', 'yoursite.ddev.site');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);

⚠️ Important: Most of the time if not all the time!, you would be experiencing login problems, such as inability to log in due to the cookie issues. from here, you need to play with the cookie settings in wp-config-local.php for example trying to set define( 'COOKIE_DOMAIN', 'your-local-ddev-site.ddev.site:447' ); which in most cases you would see the warning about the constant being already defined in wp-config.php. Then simply set these in wp-config-local.php:

define( 'ADMIN_COOKIE_PATH', '/' );
define( 'COOKIEPATH', '' );
define( 'SITECOOKIEPATH', '' );

Optional Pantheon Integration

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