What potential issues can arise when using inline frames from different domains in PHP applications?

Potential security issues can arise when using inline frames (iframes) from different domains in PHP applications, as it can lead to cross-site scripting (XSS) attacks or data leakage. To mitigate these risks, it is recommended to set the X-Frame-Options header to deny or sameorigin to prevent the browser from loading the iframe.

<?php
header("X-Frame-Options: DENY");
?>