What are the differences between using <?php, <?=, and <? in PHP code, and how can they impact compatibility with different PHP versions?

When writing PHP code, it's important to understand the differences between <?php, <?=, and <? tags. - <?php is the standard opening tag for PHP code and is supported by all PHP versions. - <?= is a shorthand for echoing variables in PHP and is supported in PHP 5.4 and later. - <? is a short opening tag that may not be enabled by default in some PHP configurations and can cause compatibility issues with older PHP versions. To ensure maximum compatibility, it's recommended to use <?php for opening PHP tags in your code.

<?php
// Your PHP code here
?>