Send data using GET method not work correctly

Im using WP 3.5.2 and WPMU. I develop one page http://baohiem.info/chon-mat-gui-vang. This page uses global $wpdb to query table _blogs.(_blogs was customized, added some fields.) When submit form, I use GET method, but, when log in, i have data ($_REQUEST; $_GET) but not log in, there're no data. Why? I don't understand what happen. Can anyone help me?

Thank you.

?php
get_header(); 
?

        form action= method=get
            input id=searchfield-cmgv type=text name=hoten placeholder=Họ và tên tư vấn viên.... size=35 value=?=$_REQUEST['hoten']?/
            !-- location--
            select name=location
                option value=-------- Tỉnh/TP --------/option
                option value=Hà Nội ?php if($_REQUEST['location']=='Hà Nội') echo 'selected';? Hà Nội/option
                option value=TP Hồ Chí Minh ?php if($_REQUEST['location']=='TP Hồ Chí Minh') echo 'selected';? TP Hồ Chí Minh/option
                !-- option value=Huế ?php if($_REQUEST['location']=='Huế') echo 'selected';? Huế/option--
                option value=Đà Nẵng ?php if($_REQUEST['location']=='Đà Nẵng') echo 'selected';? Đà Nẵng/option
                option value=Hải Phòng ?php if($_REQUEST['location']=='Hải Phòng') echo 'selected';? Hải Phòng/option
                option value=Đồng Nai ?php if($_REQUEST['location']=='Đồng Nai') echo 'selected';? Đồng Nai/option
                !-- option value=Đồng ThápĐồng Tháp/option
                option value=Gia LaiGia Lai/option --
                option value=Hà Giang ?php if($_REQUEST['location']=='Hà Giang') echo 'selected';? Hà Giang/option
                !-- option value=Hà NamHà Nam/option
                option value=Hà TĩnhHà Tĩnh/option --
                option value=Hải Dương ?php if($_REQUEST['location']=='Hải Dương') echo 'selected';? Hải Dương/option
                option value=Nghệ An ?php if($_REQUEST['location']=='Nghệ An') echo 'selected';? Nghệ An/option
                option value=Thái Nguyên ?php if($_REQUEST['location']=='Thái Nguyên') echo 'selected';? Thái Nguyên/option
                option value=Yên Bái ?php if($_REQUEST['location']=='Yên Bái') echo 'selected';? Yên Bái/option

           /select
           select name=company
               option value=-------- Công ty --------/option
               option value=Prudential ?php if($_REQUEST['company']=='Prudential') echo 'selected';? Prudential/option
               option value=Manulife ?php if($_REQUEST['company']=='Manulife') echo 'selected';? Manulife/option
               option value=AIA ?php if($_REQUEST['company']=='AIA') echo 'selected';? AIA/option
               option value=Dai-ichi Life ?php if($_REQUEST['company']=='Dai-ichi Life') echo 'selected';? Dai-ichi Life/option
               option value=ACE Life ?php if($_REQUEST['company']=='ACE Life') echo 'selected';? ACE Life/option
               option value=Bảo Việt ?php if($_REQUEST['company']=='Bảo Việt') echo 'selected';? Bảo Việt/option
               option value=Hanwha Life ?php if($_REQUEST['company']=='Hanwha Life') echo 'selected';? Hanwha Life/option
               option value=Generali ?php if($_REQUEST['company']=='Generali') echo 'selected';? Generali/option
               option value=Chưa có ?php if($_REQUEST['company']=='Chưa có') echo 'selected';? Chưa có/option
           /select
            input type=hidden value=true name=confirm /
           input id=searchbutton value=Tìm kiếm type=submit
        /form
        
           ?php
           global $wpdb;

            // lấy thông tin công ty, họ tên, location
            $company = $_GET['company'];
            $hoten = $_GET['hoten'];
            $location = $_GET['location'];

        if(!$company  !$hoten  !$location){

                // string query
                $strquery = '
                                        SELECT bh_blogs.blog_id
                                        FROM bh_blogs
                                        WHERE bh_blogs.blog_id 1
                                        AND bh_blogs.deleted =0
                                        ORDER BY bh_blogs.voted DESC        
                ';

                // get result
                $res = $wpdb-query($strquery);

                // display result
                //
                //
        } else {
           //var_dump($location); var_dump($company); var_dump($hoten);
            $strquery = '
                SELECT bh_blogs.blog_id
                FROM bh_blogs
                WHERE bh_blogs.blog_id  1 AND bh_blogs.deleted =0 ';

            if($hoten!='') $strquery .= ' AND bh_blogs.site_name LIKE %'.$hoten.'% ';
            if($company!='') $strquery .= ' AND bh_blogs.company='.$company.' ';
            if($location!='') $strquery .= ' AND bh_blogs.location='.$location.' ';

            $strquery .= ' ORDER BY bh_blogs.voted DESC ';

            //display result
            //
            //
        }  

    get_footer(); 
?

the url: http://baohiem.info/chon-mat-gui-vang/?hoten=location=Hải+Phòngcompany=Prudential not work. I can't Get['location'],Get['hoten'],Get['company']

Resolved: I use the plugin Better WP Security and it filters my URL.

To enable passing parameters like: example.com?src=SomeSourcepage=1..... Log in to you ACP. Better WP Security/System Tweak and uncheck the option Filter Suspicious Query Strings.

Note: attention with your parameters is safe for your site :)

Merry Christmas.