ms access 2007 and php

<?php
if(isset($_GET['b_no'])){
$bno=$_GET['b_no'];

include("connect.php");
$query19="select * from billing where `b_no`=$bno";

$rs19=$conn->execute($query19);

if($rs19){
$itm=explode(',',$rs19['item']);
$qty=explode(',',$rs19['qty']);
$r=count($itm);


for($i=0;$i<=$r;$i++) {
if(isset($itm[$i]) && isset($qty[$i])) {
echo "item".$itm[$i];
echo "qty".$qty[$i];
echo "<br>";
}
}

}
else {
echo "no records found";
}
}

else {
echo "enter bill no";
}
?>



this is my code for fetching records by passing a bill number . it runs fine if i pass a bill number which is present in the table but if i pass a bill number ($bno ) which is not present in the billing table then also the control goes to if statement and executes explode function and all.
basically my question is how to validate  hte select query .