title: Why the value of $_SESSION gets overwritten when the page is used from a new tab window?
body: <p>I am very new to PHP, so excuse my ignorance. The problem I'm facing is with session variables, such as the following.</p>
  
  <pre><code>$_SESSION["input_file"] = $_REQUEST['selected_file'];
  </code></pre>
  
  <p>To test the web page I've made, I open the page from multiple tabs in the firefox browser, and click submit on each. But when I do so, the session variables are getting overriden in the older submits with the newer submits. Why each web page doesn't have a unique session associated with them?</p>