title: Ensure that url was called with specific parameter
body: <p>I have a script.php that can be accessed by browser. To be able to do anything it has to be called by using script.php?abc=1<br />
  What is the best way to check if parameter was called and if not, stop the script?
  Would checking for <code>$_SERVER['REQUEST_URI']</code> be enough? Do all browsers use it?</p>
  <p>Thank you</p>