Explore event stream processing in PHP through this 42-minute conference talk from PHP UK Conference 2013. Discover how to build reactive systems using React PHP and simple functions, offering much of the power of commercial Complex Event Processing (CEP) with reduced complexity. Learn about stream operations, various window types including tumbling, periodic, and sliding windows, custom aggregate functions, and state updating. Gain insights into monitoring effectiveness and implementing semi-join window data for early pattern detection in business and finance applications. Access accompanying slides for visual reference and deeper understanding of the concepts presented.