PHP is the VBScript of the open source world. It's available on almost every web host, and it seems to be what beginners learn first. While I'm sure it's possible to write things in a safe and mantainable way, most code examples you see will be from beginners and will have problems with the OWASP top 10. You can't look to the built in libraries for inspiration beacuse they're usually poorly designed. Just because there have been success stories in a language (cold fusion and myspace, php and facebook) doesn't mean it's right for you. It took me one website and only 1000 lines of code to decide against PHP. If you've used it longer and like it, it's probably fine.