Imprime el array $navegador , con print_r($navegador); y veras que tiene mucha informacion ...
Código:
[browser_name_regex] => ^mozilla/5\.0 (windows; .*; windows nt 5\.1; .*; rv:1\..*) gecko/.* firefox/1\.5.*$
[browser_name_pattern] => Mozilla/5.0 (Windows; *; Windows NT 5.1; *; rv:1.*) Gecko/* Firefox/1.5*
[parent] => Firefox 1.5
[platform] => WinXP
[win32] => 1
[browser] => Firefox
[version] => 1.5
[majorver] => 1
[minorver] => 5
[frames] => 1
[iframes] => 1
[tables] => 1
[cookies] => 1
[javaapplets] => 1
[javascript] => 1
[css] => 2
[cssversion] => 2
[supportscss] => 1
[alpha] =>
[beta] =>
[win16] =>
[win64] =>
[backgroundsounds] =>
[authenticodeupdate] =>
[cdf] =>
[vbscript] =>
[activexcontrols] =>
[stripper] =>
[isbanned] =>
[wap] =>
[ismobiledevice] =>
[issyndicationreader] =>
[crawler] =>
[aol] =>
[aolversion] => 0
[netclr] =>
[clrversion] => 0
)
seria con $navegador['platform'] (ojo para XP da
WinXP)