title: PHP's preg_match() and preg_match_all() functions
body: <p>What do the <a href="https://www.php.net/manual/en/function.preg-match.php" rel="nofollow noreferrer">preg_match()</a> and <a href="https://www.php.net/manual/en/function.preg-match-all.php" rel="nofollow noreferrer">preg_match_all()</a> functions do and how can I use them?</p>