3v4l.org

run code in 200+ php & hhvm versions
Bugs & Features
<?php $embedCode = '<iframe width="800" > </iframe>'; echo preg_replace('/(<iframe[^>]*\swidth=")(\d+)("\s.*)/', '${1}' . '666' . '{3}', $embedCode);
based on mggKA
Output for 4.3.0 - 7.2.0
<iframe width="666{3}