PHP how to remove item from session when not in use - php

Question

On my website, I allow users to view a users information by simply clicking their name. Once they click the persons name, they can schedule the person to come to an event. When the user clicks "schedule me" I take the them full name from the "user_id" and send it as a "$_SESSION['speaker']" to the next file that pretty much checks if the user came from the last file and takes the name and uses it as the input value for the calendar. The problem I am having is that when the user didn't "click schedule" from the other file and goes to the calendar website alone, the name from the previous person they clicked stays there and I want it to be blank in case they want to put a different name. So pretty much i would access the calendar website just by typing the URL and the name would still be in the session. I want to clear the session without logging the user out so they don't see the name of the previous person they clicked. Here is some of my code
First file
$_GET['speaker'] = $_SESSION['speaker_id'];
$speaker_id = $_GET['speaker'];
$stmtSpeaker = $handler->prepare("SELECT * FROM formdata WHERE user_id= :speaker_id");
$stmtSpeaker->bindParam(':speaker_id', $speaker_id, PDO::PARAM_INT);
$stmtSpeaker->execute();
$formData = $stmtSpeaker->fetch();
if(isset($_POST['schedule_me'])){
$_SESSION['admin'] = $adminBoolean;
$_SESSION['speaker'] = $formData['fullname'];
$_SESSION['speaker_came'] = true;
header("Location: admincalendar.php");
exit;
}
Second file
$adminBoolean = $resultChecker['admin'];
if($_SESSION['speaker_came'] = true){
$speaker = $_SESSION['speaker'];
}else{
$speaker = "";
}

Answer 1

Unset will destroy a particular session variable whereas session_destroy() will destroy all the session data for that user.
It really depends on your application as to which one you should use. Just keep the above in mind.
unset($_SESSION['name']); // will delete just the name data
session_destroy(); // will delete ALL data associated with that user.

Answer 2

You can unset session variable
$adminBoolean = $resultChecker['admin'];
if($_SESSION['speaker_came'] = true){
$speaker = $_SESSION['speaker'];
}else{
unset($_SESSION['speaker']);
unset($_SESSION['speaker_came']);
$speaker = '';
}

Answer 3

You need to first get the tempkey of the element and then unset it. Try this:
if(($tempkey = array_search($speaker_id, $_SESSION['speaker'])) !== FALSE)
unset($_SESSION['speaker'][$tempkey]);