$re = '/=hyperlink\("([@\\\\\w\s\(\)\-\.\/]+\\\\([^"]+))"\)/i';
$str = '=hyperlink("\\\\share\\folder\\log\\2013\\13-05-13\\13-05-13.txt")';
$subst = "<a href=\"file:///$1\">$2</a>";
$result = preg_replace($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