Fatal error: Cannot use isset() on the result of an expression

Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead) in D:\openserver\OSPanel\domains\dg.com\vip_files\vip1.php on line 8

<?php
include_once("db.php");
$name = strip_tags(trim($_POST['name']));
$result = mysqli_query($link, "INSERT INTO `nicks_vip_1_day_table` (`name`) 
VALUES ('$name');");
if (isset($_POST('nick'))) {
  $errors = array();
  if (trim($_POST['nick']) == '') {
     $errors = 'Введите NickName';
}
if (empty($errors)) {
}else{
    echo '<div style="color:red;">'.array_shift($errors).'</div><hr>';
}

}

?>