How can the use of & instead of & help in resolving issues related to PHP variables in URLs for XHTML compliance?

Using & instead of & in URLs helps to ensure XHTML compliance because & is the proper way to represent the ampersand character in HTML. When & is used in URLs, it can cause parsing issues in XHTML because it is a reserved character. By using & instead, the URL will be correctly interpreted by the browser, avoiding any parsing errors.

$url = 'https://example.com/page.php?var1=value1&var2=value2';
echo '<a href="' . $url . '">Link</a>';