title: Page.IsPostBack equivalent in PHP
body: <p>When working on the same page which accepts Post data, it is good to know whether there is a special function like the one in Asp.NET such as <code>Page.IsPostBack</code>. Maybe I could use <code>isset($_POST)</code> but I am thinking there could be a special function for that.</p>
  
  <p>So I want to process the post data under that function give alerts during processing the post data, otherwise it is just a page request.</p>