php reload page with updated query string

The question is kind of vague, but assuming you want to reload from the client side using javascript:

window.location = "http://www.domain.com/myscript.php?p1=xyz&p2=100&p3=ghj"

Reload your page you just have to setup your variables the way you want it in the URL field

If you want to reload page with desired parameters use JS

Following script might help you

window.location = "http://www.domain.com/myscript.php?p1=xyz&p2=100&p3=ghj"
window.location = "http://www.domain.com/myscript.php?p2=200&p1=dfgb&p3=asdhahskh&etc=alotofparameters"

Now if you want to reload the page after a specific amount of time interval then you can use the following meta tag

<meta http-equiv="refresh" content="30; ,URL=http://www.metatags.info/login">

Njoy Coding. :)

Here is what I use when I want to change 1 $var value and then redirect.

function getUrlWithout($getNames){
  $url = $_SERVER['REQUEST_URI'];
  $questionMarkExp = explode("?", $url);
  $urlArray = explode("&", $questionMarkExp[1]);
  $retUrl=$questionMarkExp[0];
  $retGet="";
  $found=array();
  foreach($getNames as $id => $name){
        foreach ($urlArray as $key=>$value){
            if(isset($_GET[$name]) && $value==$name."=".$_GET[$name])
                unset($urlArray[$key]);
      }
  }
  $urlArray = array_values($urlArray);
  foreach ($urlArray as $key => $value){
      if($key<sizeof($urlArray) && $retGet!=="")
          $retGet.="&";
      $retGet.=$value;
  }
  return $retUrl."?".$retGet;
} 

This takes the url ($_SERVER['REQUEST_URI']), removes the desired values ($getNames) [which can be one or more values], and rebuilds the url. It can be used like-

$newurl = getUrlWithout(array("p2"));
header( 'Location: http://www.domain.com/'.$newurl.'&p2=100' );

Try below codes:

$varURL = 'http://www.domain.com/myscript.php?p1=xyz&p2=10&p3=ghj';
$varNEwURL = preg_replace('/p2=([0-9]*)&/', 'p2=100&', $varURL);
header('location:'.$varNEwURL);

OR

$varURL = 'http://www.domain.com/myscript.php?p1=xyz&p2=10&p3=ghj';
$varNEwURL = $varURL.'&p2=100';
header('location:'.$varNEwURL);