<?php

// check if query string is single or array
$rows = explode("&", $_SERVER['QUERY_STRING']);

if (  count( $rows ) > 1 )
    echo 'query string contains more than one query string value' ;

// Get filter from query string
// 1 parameter only
$qs = ( isset ( $_GET['filter']) )  ? htmlspecialchars( $_GET["filter"] ) :  ''  ;
echo $qs ;
// echo ( isset ( $_GET['filter']) )  ? htmlspecialchars( $_GET["filter"] ) :  ''  ;


// for multiple query string filters
$queries = array();
parse_str( $_SERVER['QUERY_STRING'], $queries);

echo '<pre>' ;
print_r( $queries ) ;
echo '</pre>' ;
exit() ;