Documentation for custom parameters.

docs/HowTo/CustomParameters.md

+# How to set custom parameters to your search
+
+Elasticsearch supports number of custom parameters which can be added to your query. Detailed explanation of each parameter can be found at [official documentation](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-body.html#_parameters_5)
+
+## Setting `timeout` parameter
+
+This option allows user to specify timeout for query execution in ["Time units"](https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#time-units).
+
+Following code
+
+```php
+$search = new Search();
+$search->setTimeout('5s');
+```
+
+would generate the query like this:
+```json
+{
+  "timeout": "5s"
+}
+```
+
+## Setting `from` and `size` parameters
+
+These parameters are usually used for pagination.
+
+Following code
+
+```php
+$search = new Search();
+$search->setSize(25);
+$search->setFrom(50);
+```
+
+would generate the query like this:
+```json
+{
+  "size": 25,
+  "from": 50
+}
+```
+
+## Setting `terminate_after` parameter
+
+This parameter can limit how many documents can be fetched from shard before query execution is terminated.
+
+Following code
+
+```php
+$search = new Search();
+$search->setTerminateAfter(1000);
+```
+
+would generate the query like this:
+```json
+{
+  "terminate_after": 1000
+}
+```
+
+## Setting `search_type` and `request_cache` parameters
+
+These parameters are different from previous ones because they have to be passed not in query's body but as query string parameters.
+
+Following code
+
+```php
+$search = new Search();
+$search->setSearchType('dfs_query_then_fetch');
+$search->setRequestCache(true);
+```
+
+would generate query string with `?search_type=dfs_query_then_fetch&request_cache=true`.
\ No newline at end of file

docs/index.md

@@ -11,6 +11,7 @@ Everything starts from the `Search` object. We recommend first to take a look at
 
 ### How to
 - [How to Search](HowTo/HowToSearch.md)
+- [How to set custom parameters to Search](HowTo/CustomParameters.md)
 - more coming soon..
 
 [1]: https://github.com/elastic/elasticsearch-php