wp-includes/class-wp-http-proxy.php:57Whether proxy connection should be used.
bool public function is_enabled() { return defined( 'WP_PROXY_HOST' ) && defined( 'WP_PROXY_PORT' ); }Introduced in 2.8.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-http-proxy.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.