This document provides a summary of hidden features in PHP as presented by Ilia Alshanetsky at the 2011 International PHP Conference. Some key features discussed include the __DIR__ magic constant for determining the path of a PHP script, the ?: operator for retrieving the first non-empty value from two expressions, new encryption functions, improvements to date parsing, using FileInfo for reliable file identification, and extensions like StatGrab and MailParse that provide system information and email parsing capabilities. The document is formatted as a slide presentation with code examples demonstrating usage of these PHP features.