try this
<?php
session_start();
function putForm2(){
$myForm = "<form name='form2' method='post' action='#'><table border='1'><tr><td>form 2 is here!<br></td></tr><tr><td><input type='text' name='txt123' id='txt123'></td></tr> <tr><td><input type='submit' name='sendtwo' id='sendtwo' value='TwoClick'></td></tr></table></form>";
return $myForm;
}
?><!DOCTYPE html>
<html>
<head><title></title>
</head>
<body>
<div id="One">
<form name="form1" method="post" action="#">
<?php echo "<input type='text' name='txt1' id='txt1'>"; // This text box is dynamically populated ?>
<input type="submit" name="sendone" id="sendone" value="OneClick">
</form>
</div>
<div id="two">
<?php
if(isset($_POST['sendone']))
{ if($_POST['txt1'] == '')
{echo 'txt1 is empty!'; return;} else {$_SESSION['txt1'] = $_POST['txt1'];}
if(isset($_SESSION['txt1']))
echo $_SESSION['txt1'];
echo putForm2();
}
if(isset($_POST['sendtwo']))
if(isset($_POST['sendtwo']))
{
if($_POST['txt123'] == '')
{
echo putForm2();
echo "Text box is empty..."; return;
}
}
?>
</div>
</body>
</html>