PHP - Pasar variables por url de un form

<form method="POST" action="http://www.miweb.com/index_new.php" name="formLogin" >

div class="login">&#65279;user name</div>

                        <div class="login">

                            <input type="text" name="username" id="id_username" value="" size="19"  maxlength="50" tabindex="1" />

                        </div>

                        <div class="login">&#65279;password</div>

                        <div class="login"><input type="password" name="password" size="19" tabindex="2" value="" maxlength="50"/></div>

<a href="javascript:document.formLogin.submit()" tabindex="5">Sign In</a>

 </form>

<div id="login_form" style='display: none' title="Login">

	<div id="status" align="left">

		<center>

			<div id="login_response" style="color: red;">

			Your session has expired. Please re-login to continue working with Fieldclimate.			</div>

		</center>

		Enter your username and password below		<form id="login" action="javascript:alert('success!');" method="post" >

		<input type="hidden" id="cur_user_name" name="cur_user_name" value="carina">

		<table>

			<tr>

				<td align="right">

					&#65279;Usuario				</td>

				<td>

					<input type="text" name="user_name" maxlength="50" tabindex="1">

				</td>

			</tr>

			<tr>

				<td align="right">&#65279;Clave</td>

				<td><input type="password" name="user_passw" maxlength="50" tabindex="2"></td>

			</tr>

			<tr>

				<td colspan="2" align="center"><input value="Login" name="Login" id="submit" type="submit" class="ui-state-default ui-corner-all" /></td>

			</tr>

		</table>

		</form>

	</div>

</div>

<!-- End  Ajax Login Form -->

<script>

	$('document').ready(function() {

		var dialogLogin = {

				bgiframe: true,

				autoOpen: false,

				width: 350,

				height: 200,

				modal: true,

				resizable: false

		};

		$('#login_form').dialog(dialogLogin);

		var str = "";

		var time = 300000;

		var busy = false;

		function check_time() {

			if ($('#login_form').dialog("isOpen") || busy == true) {

				return;

			}

			busy = true;

			$.ajax({

	    		type: "POST",

	    		url: "api/CIDIUser/CheckTime",  // Send the login info to this page

	    		data: str,

	    		dataType : "json",

	    		error : function() {busy=false;},

	    		success: function(msg){

	    				busy=false;

						if (msg.faultcode) {

						} else

	 					{

							var time_e = msg.ReturnParams.time;

		 					if (time_e == -1 || time_e<(time/1000)) {

								ajax_login();

			 				}

	 					}

	 			}

	  		});

		}

		window.setInterval(check_time, time);

		window.onfocus=check_time;

		// When the form is submitted

		$("#status > form").submit(function(){

			var str = $(this).serialize();

			$.ajax({

	    		type: "POST",

	    		url: "api/CIDIUser/Login",  // Send the login info to this page

	    		data: str,

	    		dataType : "json",

	    		error : ajax_errors,

	    		success: function(msg){

						if (msg.faultcode) {

							var login_response = msg.faultstring;

	 						$('#login_response').html(login_response);

	 						return false;

						} else

	 					{

							$('#login_form').dialog('close');

							var login_response = msg;

							var user_name=msg.ReturnParams.user_name;

							var cur_user_name = $('#cur_user_name').val();

							if (cur_user_name != user_name) {

								window.location.href='index_new.php';

								//window.location.reload();

								return false;

							}

	 					}

	 			}

	  		});

			return false;

		});

	});

</script>

<form id="login" action="javascript....