For framework suggestions: CodeIgniter or Laravel, nothing else.
But don't jump just right now. It sucks to have a framework when you don't know all the subleties of the language, so first learn php properly.
Most vulnerabilities in web applications come thanks to bad development practices, such as those cheap YouTube tutorials where they step by step spoon feed you, but it's all chewed and you ONLY end up knowing what they EXACTLY told you. I don't think nobody has ever audited these dudes btw for webdev industry's sake, so expect the worst from them. (Not to prejudice you, but that's what I've seen).
Stick to PHP.NET, and make no mistake: this is a security forum, so you'd be wise to also stick with OWASP learning programs or similar. Oh yeah, and a tenet of security: whatever you do, should be secure from the ground-up (from its architecture, design, whatever you call it), anything that has "an external plugin for security" will be most likely flawed. Not necessarily flawed, but most likely. Cheerio!
EDIT: My engrish suked.