How to display result of php file in an html file

I need help please. I create html file with 2 tabs. The first tab contains form that takes user input and submit it to php file. I want the result of the php file to be displayed in the second tab. 

HTML file
<ul class="nav">
    <li id="TAB0" class="selected"><a href="#TAB0">Run function</a></li>
    <li id="TAB1"><a href="#TAB1">Results</a></li>
    <li id="TAB2"><a href="TAB2">Help</a></li>
</ul>
<div class="content" id="CONTENT">
    <!--TAB0-->
           <div id = "TAB0" class="active">
            <div class="MainContent">
              <form id='myform' enctype='multipart/form-data' name='myForm'  method='post' action="calculateResults.php">
                      SOME INPUTS HERE
                   <p><input type='button' name="mybut" value='Run'></p>
              </form></div></div>
     <!--TAB1-->
           DISPLAY THE RESULT HERE
     <!--TAB2-->

What is done actually with the above code is display the result in a new window. The php file is already print the output result in some texts and table. I want when I click the button in the first tab to execute .php file and display the result in the second tab not in a new window.

Any help please? 
Thanks,