We have added a filterInput method which allow with single value to filter on all fields in the grid. Works only when datatype is local.
<?php 
ini_set
("display_errors",1);
require_once 
'../../../../php/demo/tabs.php';
?>
<!DOCTYPE html>
<html>
  <head>
    <title>jqGrid PHP Demo</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <link rel="stylesheet" type="text/css" media="screen" href="../../../../css/jquery-ui.css" />
    <link rel="stylesheet" type="text/css" media="screen" href="../../../../css/trirand/ui.jqgrid.css" />
    <style type="text">
        html, body {
        margin: 0;            /* Remove body margin/padding */
        padding: 0;
        overflow: hidden;    /* Remove scroll bars on browser window */
        font-size: 75%;
        }
    </style>
    <script src="../../../../js/jquery.min.js" type="text/javascript"></script>
    <script src="../../../../js/trirand/i18n/grid.locale-en.js" type="text/javascript"></script>
    <script src="../../../../js/trirand/jquery.jqGrid.min.js" type="text/javascript"></script> <script type="text/javascript">         
    $.jgrid.no_legacy_api = true;
    $.jgrid.useJSON = true;
    $.jgrid.defaults.width = "700";
    </script>
     
    <script src="../../../../js/jquery-ui.min.js" type="text/javascript"></script>
         <script src="../../../../js/trirand/jquery.jqGrid.min.js" type="text/javascript"></script> <script type="text/javascript">         
    </script>
  </head>
  <body>
      <div style="width:700px">
        <div style="margin-bottom: 5px;text-align: right;">
        <label for="search_cells">
        Search Grid: 
        </label>
        <input id="search_cells" type="search"/>
          </div>
          <?php include ("grid.php");?>
      </div>
      <br/>
      <?php tabs(array("grid.php"));?>
   </body>
</html>
grid.php.
<?php
require_once '../../jq-config.php';
// include the jqGrid Class
require_once ABSPATH."php/PHPSuito/jqGrid.php";
// include the driver class
require_once ABSPATH."php/PHPSuito/DBdrivers/jqGridPdo.php";
// Connection to the server
$conn = new PDO(DB_DSN,DB_USER,DB_PASSWORD);
// Tell the db that we use utf-8
$conn->query("SET NAMES utf8");

// Create the jqGrid instance
$grid = new jqGridRender($conn);
// Write the SQL Query

$grid->SelectCommand 'SELECT CustomerID, CompanyName, Phone, PostalCode, City FROM customers';
// set the ouput format to json
$grid->dataType 'json';
// Let the grid create the model
$grid->setColModel();
// Set the url from where we obtain the data
$grid->setUrl('grid.php');
// Set some grid options
$grid->setGridOptions(array(
    
"rowNum"=>10,
    
"rowTotal" => -1,
    
"rowList"=>array(10,20,30),
    
"sortname"=>"CustomerID",
    
"loadonce" =>true,
    
"height"=>150)
);
$code = <<<CODE
    var timer;
    $("#search_cells").on("keyup", function() {
        var self = this;
        if(timer) { clearTimeout(timer); }
        timer = setTimeout(function(){
            //timer = null;
            $("#grid").jqGrid('filterInput', self.value);
        },0);
    });
CODE;
$grid->setJSCode($code);
// Enable navigator searching
$grid->navigator true;
// Set which buttons should be visible
$grid->setNavOptions('navigator',array("add"=>false,"edit"=>false,"del"=>false,"view"=>false,"excel"=>false));
// Enjoy
$grid->renderGrid('#grid','#pager',truenullnulltrue,true);