PHP - Transferring Data Between Pages

<?php
$query2 = DB::getInstance()->query("SELECT 
                c.id as cid, c.title, c.time, 
		m.id as membersid, m.username, 
		m.member_first_name, m.member_last_name 
		FROM conversation as c, members as m
		WHERE ((c.member1='{$memberid}' 
		and c.read1='Yes' and c.removed1='No' 
		and m.id=c.member2) 
		OR (c.member2='{$memberid}' and c.read2='Yes' 
		and c.removed2='No' and m.id=c.member1)) 
		GROUP BY m.id ORDER BY m.id DESC");
?>

<table>
<tr>
	<td align="left">
		<?php echo htmlentities($result2->member_first_name); ?>
		<?php echo htmlentities($result2->member_last_name); ?>
		<?php echo "("; echo htmlentities($result2->username); echo ")"; ?>
	</td>
	<td align="right">
		<?php echo timeAgo(strtotime($result2->time)); ?>
	</td>
</tr>
<tr>
	<td colspan="2" align="left">
		<form action="" method="post">	
		<?php echo "Subject: "; ?>
		<?php echo "<input type='hidden' name='id' id='id' value='{$result2->cid}'>"; ?>
		<a href="#$result2->cid" onClick="showMessages(this.value)"><?php echo htmlentities($result2->title); ?>
		</form>
		<script src="//code.jquery.com/jquery-1.10.2.js"></script>
		<script src="js/readmessage.js"></script>
	</td>
</tr>
</table>
<div id="txtMessage"></div>

function showMessages(str)
{
if (str=="")
  {
  document.getElementById("txtMessage").innerHTML="";
  return;
  } 
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
xmlhttp.onreadystatechange=function()
  {
  if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
    document.getElementById("txtMessage").innerHTML=xmlhttp.responseText;
    }
  }
xmlhttp.open("GET","readmessage.php?q="+str,true);
xmlhttp.send();
}

?php
require 'core/memberinit.php';
$member = new Member();
include 'timeago.php';

$memberid = $member->data() ->id;

if(isset($_GET['q'])) {
	$q = html_entity_decode($_GET['q']);
	
	$req1 = DB::getInstance()->query("SELECT title, member1, member2 FROM conversation WHERE id='{$q}' AND id2='1'");
	
	foreach ($req1->results() as $dn1)
	
	if($req1->count()==1)
	{
		if(($dn1->member1=='{$memberid}') or ($dn->member2=='{$memberid}'))
		{
			if($dn1->member1=='{$memberid}')
			{
				DB::getInstance()->query("UPDATE conversation SET read1='Yes' where id='{$q}' and id2='1'");
				$user_partic = 2;
			} else {
				DB::getInstance()->query("UPDATE conversation SET read2='Yes' where id='{$q}' and id2='1'");
				$user_partic = "1";
			}
			$req2 = DB::getInstance()->query("SELECT conversation.time, conversation.message, 
						members.id as userid, members.username, members.member_first_name, members.member_last_name 
						FROM conversation, members 
						WHERE conversation.id='{$id}' AND members.id=conversation.member1 
						ORDER BY conversation.id2");
			if(isset($_POST['message']) and $_POST['message']!='')
			{
				$message = $_POST['message'];
				if(get_magic_quotes_gpc())
				{
					$message = stripslashes($message);
				}
				$message = $string(nl2br(htmlentities($message, ENT_QUOTES, 'UTF-8')));
				if(	DB::getInstance()->query("INSERT into conversation 
					(id, id2, title, member1, member2, message, time, read1, read2)
					VALUES('{$q}', '{(intval($req2->id2)+1)}', '', '{$memberid}', '', '{$message}', '.time().', '', '')") 
					and 
				DB::getInstance()->query("UPDATE conversation SET read'{$user_partic}'='Yes' WHERE id='{$q}' AND id2='1'"));
			}
			echo "<h4>";
			echo $dn1->title; 
			echo "</h4><br><br>";
			echo "<table><col width='150px'><col width='50px'><col width='150px'>";
			echo "<tr><th>Member</th><th>&nbsp</th><th>Message</th></tr>";
			
			foreach ($req2->results() as $dn2)
			{
			echo "<tr><td>";
			echo $dn2->members.member_first_name;
			echo $dn2->members.member_last_name;
			echo " (";
			echo $dn2->members.username;
			echo ")	</td><td></td><td>";
			echo timeAgo(strtotime($dn2->time));
			echo "<br>";
			echo $dn2->message;
			echo "</td></tr>";
			}
			echo "</table>";
		}
	}
}
?>

<?php
require 'core/memberinit.php';
$member = new Member();
include 'timeago.php';

$memberid = $member->data() ->id;

if(isset($_GET['q'])) {
	$q = intval($_GET['q']);

echo $q;
}
?>