PHP Session变量消失了吗？

Question

I have 3 pages, login.php, login_validate.php and userhome.php. My issue is that the login information is being correctly passed to login_validate.php, but seems to disappear when login_validate redirects to userhome.php

Any help would be appreciated.

Login.php

<form name="login" action="login_validate.php" method="post">
    Username: <input type="text" name="myusername" /><br />
    Password: <input type="password" name="mypassword" /><br />
    <input type="submit" value="Login" />
</form>

login_validate.php (I know, it's long)

<?php

  include'connect.php';

  // username and password sent from form
  if(isset($_POST['myusername']) and isset($_POST['mypassword'])){
    $myusername=$_POST['myusername'];
    $mypassword=$_POST['mypassword'];
  }else{
    header('Location:login.php?failatvalidate');
  }
  // To protect MySQL injection (more detail about MySQL injection)
  $myusername = stripslashes($myusername);
  $mypassword = stripslashes($mypassword);
  $myusername = mysql_real_escape_string($myusername);
  $mypassword = mysql_real_escape_string($mypassword);

  $mypassword = hash('sha256', $mypassword);

  $sql="SELECT * FROM users WHERE username='$myusername' and password='$mypassword'";
  $result=mysql_query($sql);

  // Mysql_num_row is counting table row
  $count=mysql_num_rows($result);

  // If result matched $myusername and $mypassword, table row must be 1 row

  if($count==1){

  // Register $myusername, $mypassword and redirect to file "userhome.php"
  $_SESSION['myusername'] = $myusername;
  $_SESSION['mypassword'] = $mypassword;

  print '<pre>';
  var_dump($_SESSION);
  print '</pre>';

  echo "<a href='userhome.php'>Home</a>";
  }
  else {
    echo "Wrong Username or Password";
  }
?>

userhome.php

<?php
  error_reporting(E_ALL ^ E_NOTICE);
  ini_set('display_errors',1);

  session_start();
  if(!isset($_SESSION['myusername'])){
    echo "error :( ";
  }else{
    echo "Logged in as ".$_SESSION['myusername']."&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp<a href='logout.php'>Log out</a><br /><br />";
  }
?>

Answer 1

You need to call session_start() in every script that uses sessions (and before the headers are sent).