Explain advanced Elasticsearch architecture and search optimization in PHP applications.

Elasticsearch provides distributed full-text search and analytics optimized for massive-scale querying and indexing.

Traditional relational databases struggle with advanced search workloads. Elasticsearch solves this using distributed inverted indexes.

Core concepts:

Instead of storing rows directly, Elasticsearch maps terms to document references.

Indexes split across distributed nodes.

Provide redundancy and parallel query execution.

Index refresh cycles allow rapid querying.

Text processing includes:

6.…