[DOCS] Fix broken link to elasticsearch-php security page

x-pack/docs/en/security/ccs-clients-integrations/http.asciidoc

@@ -54,7 +54,7 @@ specific clients, refer to
 https://github.com/elasticsearch/elasticsearch-ruby/tree/master/elasticsearch-transport#authentication[Ruby],
 http://elasticsearch-py.readthedocs.org/en/master/#ssl-and-authentication[Python],
 https://metacpan.org/pod/Search::Elasticsearch::Cxn::HTTPTiny#CONFIGURATION[Perl],
-http://www.elastic.co/guide/en/elasticsearch/client/php-api/current/_security.html[PHP],
+http://www.elastic.co/guide/en/elasticsearch/client/php-api/current/security.html[PHP],
 http://nest.azurewebsites.net/elasticsearch-net/security.html[.NET],
 http://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/auth-reference.html[JavaScript]