How can special characters like commas affect URL parsing in PHP?

Special characters like commas in URLs can affect URL parsing in PHP because they can be interpreted as delimiters or separators, causing unexpected behavior. To solve this issue, you can encode the special characters using the `urlencode()` function before including them in the URL.

$url = 'http://example.com/page.php?param=' . urlencode('special,characters');
echo $url;