title: include, include_once, require or require_once?
body: <p>I have PHP file where I have defined the server access variables as well as the <code>mysql_connect</code> and <code>mysql_select_db</code>, as this functions are regularly used in almost every page in backend, while I am using <code>include()</code> which is perfectly working for me now, which method or function would you suggest and I would like to know if there is any flaw if I use <code>include()</code> or is it safe to use it?</p>
  
  <p>Edit : Keeping in mind I'll be using <code>$_SESSION</code> variable too. </p>