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Question

When users log in, it will show logout. When users haven't logged in, echo the welcome message and show login. My code in some web pages are working. Yet, in some pages are shown both login and logout. I don't know why, please help.

<?php 


   session_start();
  if (isset($_SESSION['loginID_member']))


{

echo "Welcome, ".$_SESSION['loginID_member'];
echo "&nbsp;&nbsp;";
echo "<a href='../logout.php''>Logout</a>";

  }
   else 
{
  echo "Welcome, guest!";
echo "&nbsp;&nbsp;";
echo "<a href='member_login.php'>Login</a>";
}
?>

Answer 1

You are checking for the $_POST only. Simply replace it with $_SESSION like this:

if(isset($_SESSION['loginID_member']) {
[...]

And session_start() should be at the top of the document.

Beside this your script is not very secure, since everybody just needs to send a POST Request with the key 'loginID_member' in order to log in. Try to change your sessions 'setup'.