当我不调用取消设置它的href时，为什么我的会话变量未设置

In my PHP program I have a few links that all link to the same page. What it does is update the current site depending on my action and I send new information through a GET or if I need to unset my session.

In one link to the same page, I am calling unset($_SESSION['search']) and in the other I am calling a GET for sorting information. But when I call the GET link and not the unset link, my session variable gets reset anyways.

Everything is being done in view.php

Here is my unset link

<a href="view.php<?php unset($_SESSION['search']); ?>">View All</a>

My GET link(s)

<th><a href="view.php?id=<?php echo 'id';?>">ID</a></th>

<th><a href="view.php?id=<?php echo 'itemName';?>">Item Name</a></th>

<th><a href="view.php?id=<?php echo 'description';?>">Description</a></th>

<th><a href="view.php?id=<?php echo 'supplierCode';?>">Supplier</a></th>

<th><a href="view.php?id=<?php echo 'cost';?>">Cost</a></th>

When I call the unset link, I need it to reset the session variable. But when I call the get links, I need to keep the session variable.

What can I do to make that happen?

My php action when calling those links

if (isset($_SESSION['search'])) {

    $sql_query = "SELECT * FROM inventory WHERE description LIKE '%".$_SESSION['search']."%' ORDER BY ".$id." ASC";

    $check = true;
}


else if ($_POST && !(Trim($_POST['search']) === '')) {

    $search = $link->real_escape_string($_POST['search']);

    $_SESSION['search'] = $search;

    $sql_query = "SELECT * FROM inventory WHERE description LIKE '%".$_SESSION['search']."%' ORDER BY ".$id." ASC";

    $check = true;
}

else {
    $sql_query = "SELECT * FROM inventory ORDER BY ".$id." ASC";

}

Because the $_SESSION['search'] is always reset whenever I redirect back to view.php, the last else is always called when I press the get links even though I need it to stay!