How to protect a web application written in php from injecting external XML entities?

Question

PHP

Hello.
You need to protect your web application (written in php using Symfony 2.0.18) from injecting external XML entities. Namely, according to the recommendation, "prohibit support for external entities (External Entity), external parameters of entities (External Parameter Entity) and external DTDs (External Doctype)".
The potentially dangerous simplexml_load_string command , which is used in particular in the phpexcel module.
Is it enough to use the libxml_disable_entity_loader(true) function ? And in what place of the project to execute it?