PEEP is a server-side scripting programming language that is widely used to develop website services. However, web-based PHP applications are distributed in source code so that the security is vulnerable and weak because the lines of source code can be easily copied, modified, or used in other applications. These research aims to implement obfuscation techniques design in PHP extension code using AES algorithm. The AES algorithm recommended by NIST (National Institute of Standards and Technology) to protect the US government's national information security system. Through obfuscation technique using encryption, it is expected that programmers have an option to protect the PHP source code so that the copyright or intellectual property of the program can be protected.