Felix Arntz is a web developer who specializes in WordPress development with a focus on complex web applications, helpful plugins, and backend. In 2012, he started his business, Leaves Webdesign, to provide WordPress solutions for various clients around the world, especially in the U.S. and Germany. He also develops plugins for the WordPress plugin repository.

Besides his work, he is studying applied computer science at the Ruhr Universität Bochum in Germany and looking forward to receiving his degree in early 2016. When he is not coding, he pursues his passion for making music and playing the piano. He also loves going out and enjoying the beautiful city he lives in, playing soccer, and going to the gym. He is also a movie geek and drinks a lot of Mountain Dew.

Having never worked on any book before, he thoroughly enjoyed reviewing this book and is looking forward to help improving books on the same technology in future.

David Kryzaniak is a web application developer at Fox World Travel in Oshkosh, Wisconsin. He holds a BS in information science from the University of Wisconsin, Green Bay. While he is primarily a PHP developer, he tends to do a lot of frontend coding (CSS, JavaScript, and responsive web design) too. He spends a lot of his free time working on both freelance and open source WordPress projects. You can find out more about him at https://davekz.com.

Mario Peshev is the founder of and a WordPress architect at DevriX, a distributed WordPress development agency. He has been building software solutions with PHP, Java, and Python for more than 10 years now.

In addition to his technical background, he is an international speaker and a seasoned trainer with over 10,000 hours on stage. He has conducted training courses on web and database development and security in companies and organizations such as CERN, Saudi Aramco, VMware, and Software AG.

He is currently leading a team of WordPress engineers that builds high-end solutions using the technology. With several WordPress-driven SaaS solutions behind it, the team specializes in complex multisite projects and business-specific solutions based on the popular platform. As a WordPress contributor and active community member, he is often involved with international WordPress or web development events.

Dan Purdy started his career as a technical engineer for a top London recording studio. It was during this time that he started working with WordPress as a blogging tool for his personal projects.

Currently working for a digital innovation agency in Shoreditch, London, as a senior frontend developer, he continues to build sites with WordPress while working on a variety of projects—from product prototypes and e-commerce sites to enterprise-level web applications.

He was also the technical reviewer for Raspberry Pi Gaming, Second Edition, Packt Publishing.