How to get the display datatable value in the server side script PHP during the CSV/XLS/PDF download

How to get the display datatable value in the server side script PHP during the CSV/XLS/PDF download.

TableTools.DEFAULTS.aButtons = [ "csv", "xls", "pdf" ]; 
				
TableTools.BUTTONS.download = {
    "sAction": "text",
    "sTag": "default",
    "sFieldBoundary": "",
    "sFieldSeperator": "\t",
    "sNewLine": "<br>",
    "sToolTip": "",
    "sButtonClass": "DTTT_button_text",
    "sButtonClassHover": "DTTT_button_text_hover",
    "sButtonText": "Download",
    "mColumns": "all",
    "bHeader": true,
    "bFooter": true,
    "sDiv": "",
    "fnMouseover": null,
    "fnMouseout": null,
    "fnClick": function( nButton, oConfig ) {
      var oParams = this.s.dt.oApi._fnAjaxParameters( this.s.dt );
    var iframe = document.createElement('iframe');
    iframe.style.height = "0px";
    iframe.style.width = "0px";
    iframe.src = oConfig.sUrl+"?"+$.param(oParams);
    document.body.appendChild( iframe );
    },
    "fnSelect": null,
    "fnComplete": null,
    "fnInit": null
};				



 
var oTable = $('#example').dataTable( {
    "aoColumnDefs": [
        { "bSortable": false, "aTargets": [ 0 ] }
    ],
    "aaSorting": [[0, 'desc']],
    "sPaginationType": "full_numbers",
    
    "sDom": 'T<"clear">lfrtip',
    "oTableTools": {
        "sSwfPath": "../<?php echo "swf"; ?>/copy_csv_xls_pdf.swf",
        "aButtons": [
            {
                "sExtends": "download",
                "sButtonText": "Download CSV",
                "sUrl": "./remote.php"
            }
        ]
    },
    
    

    /*"aLengthMenu": [20,50,100,200,500,1000],*/
    
    "aLengthMenu": [[20,50,100,200,500,1000, -1], [20,50,100,200,500,1000, "All"]],
    "iDisplayLength" : 20,
    
    
    //column highlight
    "bSortClasses": false,
    "oLanguage": {
       "sSearch": "Search all columns:"
    },
    
    
}).columnFilter({ 	
    sPlaceHolder: "head:after",
    aoColumns: [ 
                
                { type: "select" },
                { type: "select" },
                { type: "text" },
                { }
                /*{ type: "select", values: [ 'Refund', 'Cancel', 'Refunded']  },*/

 ]
});

remote.php (Server side file)

print_r($_REQUEST);

// parse new querystring variable "o" to represent output_mode
$output_mode = (isset($_REQUEST["o"])) ? $_REQUEST["o"] : "json";


if ($output_mode == "csv") {
  header("Content-type: text/csv"); 
  header("Cache-Control: no-store, no-cache"); 
  header('Content-Disposition: attachment; filename="filename.csv"');  // you can change the default file name here
  
  echo csv_encode( $output["aaData"], $aColumns );  // see function below
} else {
  // default is to output json
  echo json_encode( $output );
}

/*
 * csv_encode - encode data as csv, wrapping values in quotes
 */    
function csv_encode($aaData, $aHeaders = NULL) {
  // output headers 
  $output = "";
  if ($aHeaders) $output .= '"' . implode('","', $aHeaders ) . '"'  . "\r\n";
  
  foreach ($aaData as $aRow) {
    $output .= '"' . implode('","', $aRow) . '"' . "\r\n";
  }
 
  return $output;
}
]
}); 

and why I am not able to get the value when i am set the remote.php?o=csv