What are the potential pitfalls of having whitespace or characters before <?php or after ?> in PHP scripts?

Having whitespace or characters before <?php or after ?> in PHP scripts can cause unwanted output or errors, especially when trying to send headers or set cookies. To avoid this issue, ensure that there is no whitespace or characters before <?php and after ?> in your PHP scripts.

&lt;?php
// Your PHP code here
?&gt;