如何使用新URL重新加载PHP页面？

I have a page index.php of my website abc.com having some internal links e.g. contactus, aboutus etc on it.

Kindly guide me how is it possible that when someone clicks on a link (say contactus) of the page index.php, then request should go to index.php. But index.php should reload itself with the new url i.e. abc.com/contactus.

Hope It Works As You Want

on link menu declare links like

<a href="index.php?link=contact_us">Contact Us</a>

when someone click on the link then

on index.php

if(isset($_GET['link']))
{
 $link =$_GET['link'];
     if($link == 'contact_us')
     {
      header("location:contact_us.php");
     }
}

//Contact us link
<a href="index.php?redirect_url=contact_us">Contact Us</a>

//Javascript code
function getParameterByName(name, url) {
    if (!url) url = window.location.href;
    name = name.replace(/[\[\]]/g, "\\$&");
    var regex = new RegExp("[?&]" + name + "(=([^&#]*)|&|#|$)"),
        results = regex.exec(url);
    if (!results) return null;
    if (!results[2]) return '';
    return decodeURIComponent(results[2].replace(/\+/g, " "));
}

var redirect_url = getParameterByName('redirect_url');

//will redirect to contact us page after 3 seconds. You can change it as per your requirement
if(redirect_url){
    setTimeout(function(){ window.location.href = redirect_url; }, 3000);    
}

<?php
  /*we will use this this function ob_start() in the first of php page   to redirect the users after your submit data 
ob -> output buffering */
   ob_start();
 ?>

<!--for example -->
<?php
/*write this function in the first of php page*/
ob_start();
?>


<?php
    /*write your Query here after you write your query  you will write the page that you will direct the users for example */
        header('location:index.php');
     }  ?>