Clase Final PHP

<form action="directorio.php" method="get">
<div>Nombre<input name="nombre" size="50"></div>
<div>Apellido<input name="apellido" size="50"></div>
<div>Direccion<input name="direccion" size="50"></div>
<div>Telefono<input name="telefono" size="50"></div>
<div>Email<input name="email" size="50"></div>
<div><input type="submit" name="boton" value="guardar"></div>

</form>



<?php
require_once "conexion.php";
if(isset($_GET["boton"])){
$a=$_GET["nombre"];
$b=$_GET["apellido"];
$c=$_GET["direccion"];
$d=$_GET["telefono"];
$e=$_GET["email"];
$sql="INSERT INTO directorio VALUES(NULL,'$a','$b','$c','$d','$e')";
mysql_query($sql, $conexion) or die(mysql_error());
echo "Registro Agregado Correctamente";


}

$queDir = "SELECT * FROM directorio ORDER BY nombre ASC";
$resDir = mysql_query($queDir, $conexion) or die(mysql_error());
$totDir = mysql_num_rows($resDir);

if ($totDir> 0) {
echo "<table border=1><th>id</th><th>Nombre</th><th>Apellido</th><th>Direccion</th><th>Telefono</th><th>Email</th><th>Borrar</th><th>Modificar</th>";
while ($rowDir = mysql_fetch_array($resDir)) {
$a=$rowDir[0];
$linea="<tr><td>$a</td><td>$rowDir[1]</td><td>$rowDir[2]</td><td>$rowDir[3]</td><td>$rowDir[4]</td><td>$rowDir[5]</td><td></td><td></td>";
echo $linea;
}
}








?>