Prueba asi:
Código PHP:
<?php
mysql_connect("localhost","root");
$sql_aux = $_POST['VB'];
$sql_aux1 = $_POST['FECHA'];//
$sql_aux2 = $_POST['DESC'];
$sql = " SELECT VB, count( Numero_Solicitud ) AS total_unitario";
$sql.= " FROM permiso_usuario";
$sql.= " WHERE VB ='sql_aux'";
$sql.= " GROUP BY VB ORDER BY Fecha_Inicio desc";
$result=mysql_db_query("Biblioteca", $sql );
if(isset($result) && mysql_num_rows($result)>0)
{
while ($row=mysql_fetch_array($result))
{
echo $row["VB"];
echo $row["total_unitario"];
}
}
?>