I agree with tony here, the best way is to check for their security level. You would need to have a users table in the sql with a column representing their security level. You would need to assign a default, such as "0" for that column, then that value increases by one each time on specific users when there is higher access to grant.
Lets say you have a usersystem that uses an sql table called "users".
Using their userid, you query their info in the database, then establish whether or not to show them the specific content or not, based on their security level
For this example, I'm using "$user['userid']"
There may already be a variable like this to identify your users if you are integrating your script into an existing php system. Otherwise, you will need to develop a register/login system that handles sessions.
Follow the comments below, introduced by "//" for more information and feel free to reply with any questions you have.
PHP Code:
//Using their userid ($user['userid']) I can grab all their information from the database
if($user_arr = mysql_query("SELECT * FROM users WHERE userid ='" . $user['userid'] . "'"))
{
//I now use "$userinfo" as the variable to display any of their information
//NOTE: one of the SQL columns for their username contains their access
//level. This is labed as "access_level" but can be named anything
$userinfo = mysql_fetch_array($user_arr);
//I now see if their access level is equal to the required level to see the
//content. If they have access, the content shows. If they don't, the content
//is skipped from being displayed
if($userinfo['access_level'] == '3') //'3' could be any access number you want
{
// Show Permissible Content Here or Skip Me
}
}