PHP Cookbook
David Sklar & Adam Trachtenberg
Mastering Linux - Fundamentals
Paul Cobbaut
Cisco Certified CyberOps Associate 200-201 Certification Guide
Glen D. Singh
CompTIA Linux+ and LPIC-1 Guide to Linux Certification - 6th ...
Jason Eckert
Mastering Linux - Networking
Mastering Linux - System Administration
Mastering Linux - Servers