$re = '/(?:<[^\/]*?.*?<\/.*?>)|(:\/)/';
$str = 'not feeling well today :/ check out this link <a href="http://example.com">http://example.com</a>';
$subst = "xxxxxxxxx";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php