PHP isset $ _session等于string

So guys I'm new to PHP OOP

I make Login with Roles, and make function(checkrole) for knowing what role it is.

This is how my function looks like

public static function hasadmin()
{
  if(session_id() == '') {
  session_start();
  }
  if(isset($_SESSION['role']) == 'A') {
    return true;
  }
}

and call it into navbar partial :

<?php if (helper::login() == true && helper::hasadmin() == true) { ?>
<li style="float:ight"><a href="?controller=auth&action=logout">Logout</a></li>
<li><a href="?controller=admin&action=petugas">Petugas</a></li>
<li><a href="?">Laporan</a></li>

Function helper::login works perfectly. Every time I login with another role the partial (petugas, laporan) still comes out.

isset returns a boolean. Run the isset and check the actual value.

if(isset($_SESSION['role']) && $_SESSION['role'] == 'A') {