$re = '/(^<.+?name=)".+?"(.+? linkedscene=)"(.+?)"(.+\>)/m';
$str = '<hotspot name="xxxxx" style="hs_circle" ath="150.712" atv="13.351" linkedscene="landing2" tag="Landing" />';
$subst = "$1\"$3\"$2\"$3\"$4";
$result = preg_replace($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