Display results from DB using variables.

Greetings all,
I am working on a computer based test application, where when the student logs in to test the test, the questions should come from the subjects the student was registered for.

I have tried using SESSION variable to hold the registered subjects and pass them to the query that will fetch the questions,but won't work.

here is a snippet my php code so far,
<?php


<?php

//confirm session
if(isset($_SESSION['user'])){ echo $_SESSION['user'];}

else{die("Session not started");}
//get student's details using session variables
$confirmuser=mysql_query("select * from students where username='$user' ") or die(mysql_error());
while($confirm=mysql_fetch_array($confirmuser)){ec ho"<br/>";
echo $confirm['surname'].'<br/>';
echo $confirm['firstname'].'<br/>';;
echo $_SESSION['subject1'] =$confirm['subject1'].'<br/>';
echo $_SESSION['subject2']=$confirm['subject2'].'<br/>';
echo $_SESSION['subject3']=$confirm['subject3'].'<br/>';
echo $_SESSION['subject4'] =$confirm['subject4'].'<br/>';





echo '<br/>';
$fourthsubject=$_SESSION['subject2'];

echo $fourthsubject. '<br/>';

function fourth(){ global $fourthsubject;
$bend=mysql_query("select * from $subject3 ") or die(mysql_error());
while($rase=mysql_fetch_array($bend)){
echo $rase['question'];}
;}

fourth();
}
?>



The above code is displaying this error message (You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '
' at line 1)