How to get and change URL variable PHP

Try with the below expression, It Should Work

preg_replace("#&d=.*&#", '&d=newvalue&', $_SERVER['REQUEST_URI'])

To remove repeated addition of query parameter do the below

// parse the url
$pathInfo = parse_url($_SERVER['REQUEST_URI']);
$queryString = $pathInfo['query'];
// convert the query parameters to an array
parse_str($queryString, $queryArray);
// add the new query parameter into the array
$queryArray['d'] = 1;
// build the new query string
$newQueryStr = http_build_query($queryArray);

// construct new url
?>
<a href="<?php echo $pathInfo['host'].'?'.$newQueryStr;?>">LINK 1</a>

$query = $_GET;
// replace parameter(s)
$query['d'] = 'new_value';
// rebuild url
$query_result = http_build_query($query);
// new link
<a href="<?php echo $_SERVER['PHP_SELF']; ?>?<?php echo $query_result; ?>">Link</a>

modify_url_query($url, array('limit' => 50));

My function for modifying query in url

function modify_url_query($url, $mod){

$purl = parse_url($url);

$params = array();

if (($query_str=$purl['query']))
{
    parse_str($query_str, $params);

    foreach($params as $name => $value)
    {
        if (isset($mod[$name]))
        {
            $params[$name] = $mod[$name];
            unset($mod[$name]);
        }
    }
}        

$params = array_merge($params, $mod);

$ret = "";

if ($purl['scheme'])
{
    $ret = $purl['scheme'] . "://";
}    

if ($purl['host'])
{
    $ret .= $purl['host'];
}    

if ($purl['path'])
{
    $ret .= $purl['path'];
}    

if ($params)
{
    $ret .= '?' . http_build_query($params);
}    


if ($purl['fragment'])
{
    $ret .= "#" . $purl['fragment'];
}        

return $ret;

}