WP_Http::processHeaders( string|array $headers, string $url = '' ): array

public static function processHeaders( $headers, $url = '' ) { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid
	// Split headers, one per array element.
	if ( is_string( $headers ) ) {
		// Tolerate line terminator: CRLF = LF (RFC 2616 19.3).
		$headers = str_replace( "\r\n", "\n", $headers );
		/*
		 * Unfold folded header fields. LWS = [CRLF] 1*( SP | HT ) <US-ASCII SP, space (32)>,
		 * <US-ASCII HT, horizontal-tab (9)> (RFC 2616 2.2).
		 */
		$headers = preg_replace( '/\n[ \t]/', ' ', $headers );
		// Create the headers array.
		$headers = explode( "\n", $headers );
	}

	$response = array(
		'code'    => 0,
		'message' => '',
	);

	/*
	 * If a redirection has taken place, The headers for each page request may have been passed.
	 * In this case, determine the final HTTP header and parse from there.
	 */
	for ( $i = count( $headers ) - 1; $i >= 0; $i-- ) {
		if ( ! empty( $headers[ $i ] ) && ! str_contains( $headers[ $i ], ':' ) ) {
			$headers = array_splice( $headers, $i );
			break;
		}
	}

	$cookies    = array();
	$newheaders = array();
	foreach ( (array) $headers as $tempheader ) {
		if ( empty( $tempheader ) ) {
			continue;
		}

		if ( ! str_contains( $tempheader, ':' ) ) {
			$stack   = explode( ' ', $tempheader, 3 );
			$stack[] = '';
			list( , $response['code'], $response['message']) = $stack;
			continue;
		}

		list($key, $value) = explode( ':', $tempheader, 2 );

		$key   = strtolower( $key );
		$value = trim( $value );

		if ( isset( $newheaders[ $key ] ) ) {
			if ( ! is_array( $newheaders[ $key ] ) ) {
				$newheaders[ $key ] = array( $newheaders[ $key ] );
			}
			$newheaders[ $key ][] = $value;
		} else {
			$newheaders[ $key ] = $value;
		}
		if ( 'set-cookie' === $key ) {
			$cookies[] = new WP_Http_Cookie( $value, $url );
		}
	}

	// Cast the Response Code to an int.
	$response['code'] = (int) $response['code'];

	return array(
		'response' => $response,
		'headers'  => $newheaders,
		'cookies'  => $cookies,
	);
}