How can whitespace and syntax errors impact PHP session functionality?

Whitespace and syntax errors can impact PHP session functionality by causing the code to not execute properly, leading to session variables not being set or retrieved correctly. To solve this issue, ensure that there are no unnecessary whitespace characters before or after the opening and closing PHP tags, and make sure that the syntax of the code is correct.

<?php
session_start();

$_SESSION['user'] = 'John Doe';
echo $_SESSION['user'];
?>