title: Executing multiple exec() from PHP
body: <p>Situation:</p>
  
  <p>I have a PHP application where I need to get some output from <code>exec()</code> commands.
  <code>exec()</code> commands are used on different locations throughout the application.</p>
  
  <p>When a user opens multiple pages in the same browser, the <code>exec()</code> commands are allways executed sequentially; If a user opens a second page, the second page waits for the <code>exec()</code> command of the first page to finish, before executing.
  If I open a second page in a different browser, or in incognito, this problem does not occur.</p>
  
  <pre><code>Example test code:
  $exec = "notepad.exe"
  $data = shell_exec($exec);
  echo $data;
  </code></pre>
  
  <p>When running this code in the browser, the browser waits for the notepad process to close. When running the script a second time simultaniously, the second notepad process is only started when the first one is closed, unless it's ran from a different browser.</p>
  
  <p>Question:
  How can I run multiple <code>exec()</code> commands simultaneously from the same browser (in different tabs) while still beeing able to catch the output.</p>
  
  <p>Tested on Apache 2.4 running PHP 5.4.7</p>