1[[http-meta-data]]
2=== HTTP Meta Data
3
4By default, the client sends some meta data about the HTTP connection using
5custom headers.
6
7You can disable or enable it using the following methods:
8
9
10==== Elastic Meta Header
11
12The client sends a `x-elastic-client-meta` header by default.
13This header is used to collect meta data about the versions of the components
14used by the client. For instance, a value of `x-elastic-client-meta` can be
15`es=7.14.0-s,php=7.4.11,t=7.14.0-s,a=0,cu=7.68.0`, where each value is the
16version of `es=Elasticsearch`, `t` is the transport version (same of client),
17`a` is asyncronouts (`0=false` by default) and `cu=cURL`.
18
19If you would like to disable it you can use the `setElasticMetaHeader()`
20method, as follows:
21
22[source,php]
23----
24$client = Elasticsearch\ClientBuilder::create()
25    ->setElasticMetaHeader(false)
26    ->build();
27----
28
29==== Include port number in Host header
30
31This is a special setting for the client that enables the port in the
32Host header. This setting has been introduced to prevent issues with
33HTTP proxy layers (see issue https://github.com/elastic/elasticsearch-php/issues/993[#993]).
34
35By default the port number is not included in the Host header.
36If you want you can enable it using the `includePortInHostHeader()` function,
37as follows:
38
39[source,php]
40----
41$client = Elasticsearch\ClientBuilder::create()
42    ->includePortInHostHeader(true)
43    ->build();
44----
45
46==== Send the API compatibility layer
47
48Starting from version 7.13, {es} supports a compatibility header in
49`Content-Type` and `Accept`. The PHP client can be configured to emit the following HTTP headers:
50
51[source]
52----
53Content-Type: application/vnd.elasticsearch+json; compatible-with=7
54Accept: application/vnd.elasticsearch+json; compatible-with=7
55----
56
57which signals to {es} that the client is requesting 7.x version of request and response
58bodies. This allows upgrading from 7.x to 8.x version of Elasticsearch without upgrading
59everything at once. {es} should be upgraded first after the compatibility header is
60configured and clients should be upgraded second.
61
62To enable this compatibility header, you need to create an `ELASTIC_CLIENT_APIVERSIONING`
63environment variable and set it to `true` or `1`, before the `Client` class initialization.
64
65In PHP you can set this environment variable as follows:
66
67[source,php]
68----
69putenv("ELASTIC_CLIENT_APIVERSIONING=true");
70----
71