const div_content="#containerMain";
const img_loading="<div id='loading'><img src='images/loading.gif' /></div>";

function LoadContent(namecontent){
     $.ajax({
      url: base_url_include+namecontent,
      context: document.body,
      dataType: "html",
      cache: true,
      beforeSend: function(){
        $(div_content).html(img_loading);
      },
      success: function(html){
        $(div_content).html(html);
      }
    });
}

function load by ajax

ajax, php

PHP