Undefined index in php when executing sql statement

I am getting an error when I execute this query in php:

SELECT hit.timestamp, 
       hit.id, 
       config.Name, 
       hit.meter_id, 
       levels.LevelName, 
       pos.sm_pos, 
       hit.hit_value 
FROM   hit 
       INNER JOIN config 
               ON hit.id = config.id 
       INNER JOIN levels 
               ON hit.meter_id = levels.id 
       INNER JOIN POS 
               ON pos.id = hit.id 
       INNER JOIN controllers 
               ON pos.controller_id = controllers.id; 

Problem is that I am getting undefined index on each column in my select statement except the first one. Fist one is not giving me error and it gives me data normally. Other are giving errors.

Any idea what is wrong? And what I need to change?

EDIT: This query is used when using DataTables script. So fully php code is this when using this script:

<?php
    /*
     * Script:    DataTables server-side script for PHP and MySQL
     * Copyright: 2010 - Allan Jardine
     * License:   GPL v2 or BSD (3-point)
     */

    /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
     * Easy set variables
     */

    /* Array of database columns which should be read and sent back to DataTables. Use a space where
     * you want to insert a non-database field (for example a counter or static image)
     */
    $aColumns = array( 'hit.timestamp','hit.id', 'config.Name', 'hit.meter_id','levels.LevelName','pos.sm_pos','hit.hit_value'  );

    /* Indexed column (used for fast and accurate table cardinality) */
    $sIndexColumn = "hit.id";

    /* DB table to use */
    $sTable = "hit 
       INNER JOIN config 
               ON hit.id = config.id 
       INNER JOIN levels 
               ON hit.meter_id = levels.id 
       INNER JOIN POS 
               ON pos.id = hit.id 
       INNER JOIN controllers 
               ON pos.controller_id = controllers.id";

    /* Database connection information */
    $gaSql['user']       = "";
    $gaSql['password']   = "";
    $gaSql['db']         = "";
    $gaSql['server']     = "localhost";


    /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
     * If you just want to use the basic configuration for DataTables with PHP server-side, there is
     * no need to edit below this line
     */

    /* 
     * MySQL connection
     */
    $gaSql['link'] =  mysql_pconnect( $gaSql['server'], $gaSql['user'], $gaSql['password']  ) or
        die( 'Could not open connection to server' );

    mysql_select_db( $gaSql['db'], $gaSql['link'] ) or
        die( 'Could not select database '. $gaSql['db'] );


    /* 
     * Paging
     */
    $sLimit = "";
    if ( isset( $_GET['iDisplayStart'] ) && $_GET['iDisplayLength'] != '-1' )
    {
        $sLimit = "LIMIT ".mysql_real_escape_string( $_GET['iDisplayStart'] ).", ".
            mysql_real_escape_string( $_GET['iDisplayLength'] );
    }


    /*
     * Ordering
     */
    $sOrder = "";
    if ( isset( $_GET['iSortCol_0'] ) )
    {
        $sOrder = "ORDER BY  ";
        for ( $i=0 ; $i<intval( $_GET['iSortingCols'] ) ; $i++ )
        {
            if ( $_GET[ 'bSortable_'.intval($_GET['iSortCol_'.$i]) ] == "true" )
            {
                $sOrder .= $aColumns[ intval( $_GET['iSortCol_'.$i] ) ]."
                    ".mysql_real_escape_string( $_GET['sSortDir_'.$i] ) .", ";
            }
        }

        $sOrder = substr_replace( $sOrder, "", -2 );
        if ( $sOrder == "ORDER BY" )
        {
            $sOrder = "";
        }
    }


    /* 
     * Filtering
     * NOTE this does not match the built-in DataTables filtering which does it
     * word by word on any field. It's possible to do here, but concerned about efficiency
     * on very large tables, and MySQL's regex functionality is very limited
     */
    $sWhere = "";
    if ( isset($_GET['sSearch']) && $_GET['sSearch'] != "" )
    {
        $sWhere = "WHERE (";
        for ( $i=0 ; $i<count($aColumns) ; $i++ )
        {
            if ( isset($_GET['bSearchable_'.$i]) && $_GET['bSearchable_'.$i] == "true" )
            {
                $sWhere .= $aColumns[$i]." LIKE '%".mysql_real_escape_string( $_GET['sSearch'] )."%' OR ";
            }
        }
        $sWhere = substr_replace( $sWhere, "", -3 );
        $sWhere .= ')';
    }

    /* Individual column filtering */
    for ( $i=0 ; $i<count($aColumns) ; $i++ )
    {
        if ( isset($_GET['bSearchable_'.$i]) && $_GET['bSearchable_'.$i] == "true" && $_GET['sSearch_'.$i] != '' )
        {
            if ( $sWhere == "" )
            {
                $sWhere = "WHERE ";
            }
            else
            {
                $sWhere .= " AND ";
            }
            $sWhere .= $aColumns[$i]." LIKE '%".mysql_real_escape_string($_GET['sSearch_'.$i])."%' ";
        }
    }


    /*
     * SQL queries
     * Get data to display
     */
    $sQuery = "
        SELECT SQL_CALC_FOUND_ROWS ".str_replace(" , ", " ", implode(", ", $aColumns))."
        FROM   $sTable
        $sWhere
        $sOrder
        $sLimit
    ";
    $rResult = mysql_query( $sQuery, $gaSql['link'] ) or die(mysql_error());

    /* Data set length after filtering */
    $sQuery = "
        SELECT FOUND_ROWS()
    ";
    $rResultFilterTotal = mysql_query( $sQuery, $gaSql['link'] ) or die(mysql_error());
    $aResultFilterTotal = mysql_fetch_array($rResultFilterTotal);
    $iFilteredTotal = $aResultFilterTotal[0];

    /* Total data set length */
    $sQuery = "
        SELECT COUNT(".$sIndexColumn.")
        FROM   $sTable
    ";
    $rResultTotal = mysql_query( $sQuery, $gaSql['link'] ) or die(mysql_error());
    $aResultTotal = mysql_fetch_array($rResultTotal);
    $iTotal = $aResultTotal[0];


    /*
     * Output
     */
    $output = array(
        "sEcho" => intval($_GET['sEcho']),
        "iTotalRecords" => $iTotal,
        "iTotalDisplayRecords" => $iFilteredTotal,
        "aaData" => array()
    );

    while ( $aRow = mysql_fetch_array( $rResult ) )
    {
        $row = array();
        for ( $i=0 ; $i<count($aColumns) ; $i++ )
        {
            if ( $aColumns[$i] == "version" )
            {
                /* Special output formatting for 'version' column */
                $row[] = ($aRow[ $aColumns[$i] ]=="0") ? '-' : $aRow[ $aColumns[$i] ];
            }
            else if ( $aColumns[$i] != ' ' )
            {
                /* General output */
                $row[] = $aRow[ $aColumns[$i] ];
            }
        }
        $output['aaData'][] = $row;
    }

    echo json_encode( $output );
?>

This last part when outputing is using $row[] = $aRow[ $aColumns[$i] ]; and I think this is where problem is as I am using table.column type in the select statement. And funny thing is that my first column from select statement is going trough and I am getting the values. And others are giving me undefined index.