hidden field problem

[aayatoos]

i have three page.
in the first page , the user will enter information in the textboxs and will pass them to the second page that will enter the information in the database and then will go otamatically to the third page that the user wil browse for the pic and will enter the name of the pic in the database.
the problem is that i want the subject id equal to the pictures' id
how can i pass the subject id to the third page and in which page the subject id should be hidden
note:
the subject id is auto-increment and the user have no way to cotrol it

[nelustr]

Check this:

http://xtrax.ro/php/hidden/

// index.php
<form method="POST">
<?php
  if (intval($pag)==0) $pag=1;
	if ($send=="Next page"){
		 $pag=2;
		 }
	switch ($pag){
	  case "1" : {include ("pag1.inc.php"); break;}
	  case "2" : {echo "<input type=\"hidden\" name=\"info\" value=\"$info\">"; echo "<input type=hidden name=pag value=3>"; include ("pag2.inc.php"); break;}
	  case "3" : {include ("pag3.inc.php"); break;}
		}				
?>
</form>

// pag1.inc.php
<center><B>First page</B></center>
<center>
  <B>Info:</B>
	<input type="text" name="info">
	<input type="submit" name="send" value="Next page">
</center>

// pag2.inc.php

<center><B>Second page</B>
<?php
  echo "Information from the first page:$info<BR />";
	echo "Add your code here to update the database";
?> 
<input type="submit" name="send" value="Last page">
</center>

// pag3.inc.php
<center><B>Third page</B></center>
<?php
  echo "Information from the first page:$info<BR />";
	echo "Add your code here to upload the picture";
?>