title: What security issues should I look out for in PHP
body: <p>I just starting out learning PHP, I've been developing web apps in ASP.Net for a long time. I was wondering if there are any PHP specific security mistakes that I should be looking out for.</p>
  
  <p>So, my question is what are the top security tips that every PHP developer should know?</p>
  
  <p>Please keep it to one tip per answer so people can vote up/down effectively.</p>