wp-includes/Requests/src/Proxy/Http.php:151Add extra headers to the request before sending
$outstring public function fsockopen_header(&$out) { $out .= sprintf("Proxy-Authorization: Basic %s\r\n", base64_encode($this->get_auth_string())); }Introduced in 1.6. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/Requests/src/Proxy/Http.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.