Al principio de cada página debes poner
session_start();
Antes que ninguna otra cosa, obvio dentro de php.
En tu caso
Código:
index.php
<?php
session_start();
$id=session_id();;
if (empty($id)==false ){
session_name ($id);
session_call();
}
echo "<DIV id= id style='visibility:visible;overflow:hidden;position :absolute;z-index:87;left:674px;top:50px;'>";
if (strcmp($_SESSION['aut'],1) == 0){
$nom=$_SESSION['nombre'];
echo "<font face='Verdana' size='3'>Bienvenido Sr. $nom </font>";
}else{
echo "<font face='Verdana' size='2'>";
echo "<FORM NAME ='form1' METHOD ='post' ACTION = 'usuarios.php'>";
echo "<INPUT TYPE = 'TEXT' VALUE ='' STYLE='font-family: Verdana; font-size: 12px;' NAME= 'username' >";
echo "<INPUT TYPE = 'password' VALUE ='' STYLE='font-family: Verdana; font-size: 12px;' NAME = 'pwd'>";
echo "<INPUT TYPE = 'Submit' Name = 'Submit1' STYLE='font-family: Verdana; font-size: 12px;' VALUE = 'Iniciar Sesion'>";
echo "</FORM>";
echo "</font>";
}
echo "</DIV>";
?>
usuarios.php
<?php
session_start();
$username = $_POST['username'];
$pwd = $_POST['pwd'];
$conexion = mysql_connect("localhost", "web", "1234");
mysql_select_db("pueblo", $conexion);
$result = mysql_query("SELECT * FROM usuarios where usu='" . $username ."' and pwd='" . $pwd . "'");
while($row = mysql_fetch_array($result)){
session_register($row['id_usu']);
session_name ($row['id_usu']);
session_start();
$_SESSION['aut']= 1;
$_SESSION['nombre']= $row['apel1'];
header('Location: index.php?id=' . $row['id_usu']);
}
mysql_close($conexion);
?>