regular expressions - extract a string

[sde]

i need to extract the version number out of the $_SERVER['HTTP_USER_AGENT'] with php.

for example .. the string might look like this:

Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1) Opera 7.11 [en]

i need to find and extract "Opera 7.11" out of there.

For this senerio, lets say that Opera will always preceed the version number.

Opera [0-9].[0-9]{2}

some expression like that .. but i'm not sure how to get the version number into a variable.

any ideas?

[sde]

no regex .. here's the function:

PHP Code:

<?
function getVersion($preceeding,$version_length)
{
  $start=strpos($_SERVER['HTTP_USER_AGENT'],$preceeding);
  $start=$start+strlen($preceeding);
  return substr($_SERVER['HTTP_USER_AGENT'],$start,$version_length);
}
?>