Learn C, there's plenty of open source C code strictly related to security, from OpenSSL, to OpenSSH, to the Linux kernel.
Learn full stack web programming (SQL, a language, html+js). As for the language, PHP could be good as there's a lot of history of (in)security, but I definitely recommend learning a framework - I like yii (yes it is), but choose any. Studying a framework is useful to learn how much things could go wrong, if not done properly (SQL injection, XSS injection, ...).
Learn C, there's plenty of open source C code strictly related to security, from OpenSSL, to OpenSSH, to the Linux kernel.
Learn full stack web programming (SQL, a language, html+js). As for the language, PHP could be good as there's a lot of history of (in)security, but I definitely recommend learning a framework - I like yii (yes it is), but choose any. Studying a framework is useful to learn how much things could go wrong, if not done properly (SQL injection, XSS injection, ...).