wp-includes/class-wp-network.php:306Sets the cookie domain based on the network domain if one has not been populated.
private function _set_cookie_domain() { if ( ! empty( $this->cookie_domain ) ) { return; } $domain = parse_url( $this->domain, PHP_URL_HOST ); $this->cookie_domain = is_string( $domain ) ? $domain : $this->domain; if ( str_starts_with( $this->cookie_domain, 'www.' ) ) { $this->cookie_domain = substr( $this->cookie_domain, 4 ); } }Introduced in 4.4.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-network.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.