<script language="javascript">
	//detección del navegador
	var BrowserDetect = {
		   init: function () {
			  this.browser = this.searchString(this.dataBrowser) || "unknown";
			  this.version = this.searchVersion(navigator.userAgent) || this.searchVersion(navigator.appVersion) || "unknown";
			  this.OS = this.searchString(this.dataOS) || "an unknown OS";
		   },
		searchString: function (data) {
		   for (var i=0;i<data.length;i++) {
			  var dataString = data[i].string;
			  var dataProp = data[i].prop;
			  this.versionSearchString = data[i].versionSearch || data[i].identity;
			  if (dataString) {
				 if (dataString.indexOf(data[i].subString) != -1)
					return data[i].identity;
			  }
			  else if (dataProp)
			  return data[i].identity;
		   }
		},
		searchVersion: function (dataString) {
		   var index = dataString.indexOf(this.versionSearchString);
		   if (index == -1) return;
		   return parseFloat(dataString.substring(index+this.versionSearchString.length+1));
		},
		dataBrowser: [
		{
		   string: navigator.vendor,
		   subString: "Apple",
		   identity: "Safari"
		},
		{
		   prop: window.opera,
		   identity: "Opera"
		},
		{
		   string: navigator.vendor,
		   subString: "iCab",
		   identity: "iCab"
		},
		{
		   string: navigator.vendor,
		   subString: "KDE",
		   identity: "Konqueror"
		},
		{
		   string: navigator.userAgent,
		   subString: "Firefox",
		   identity: "Firefox"
		},
		{
		   string: navigator.vendor,
		   subString: "Camino",
		   identity: "Camino"
		},
		{ // for newer Netscapes (6+)
		   string: navigator.userAgent,
		   subString: "Netscape",
		   identity: "Netscape"
		},
		{
		   string: navigator.userAgent,
		   subString: "MSIE",
		   identity: "Explorer",
		   versionSearch: "MSIE"
		},
		{
		   //esta parte reconoce el chrome
		   string: navigator.userAgent,
		   subString: "Gecko",
		   identity: "Chrome", //Mozilla
		   versionSearch: "rv"
		},
		{ // for older Netscapes (4-)
		   string: navigator.userAgent,
		   subString: "Mozilla",
		   identity: "Netscape",
		   versionSearch: "Mozilla"
		}
		],
		dataOS : [
		{
		   string: navigator.platform,
		   subString: "Win",
		   identity: "Windows"
		},
		{
		   string: navigator.platform,
		   subString: "Mac",
		   identity: "Mac"
		},
		{
		   string: navigator.platform,
		   subString: "Linux",
		   identity: "Linux"
		}
	]
 
	};
	BrowserDetect.init();
 
	//estilos de cada navegador
	if (BrowserDetect.browser == "Firefox") {
		document.write("<LINK REL='stylesheet' HREF='../css/content.css' TYPE='text/css'>");
	} else {
 
		if (BrowserDetect.browser == "Explorer"){
			   if (BrowserDetect.version>=7){
				  document.write("<LINK REL='stylesheet' HREF='../css/ie7.css' TYPE='text/css'>");
			   }
		} else {
 
			if (BrowserDetect.browser == "Opera"){
					  if (BrowserDetect.version<9){
						 document.write("<LINK REL='stylesheet' HREF='../css/opera.css' TYPE='text/css'>");
					  }else{
						 document.write("<LINK REL='stylesheet' HREF='../css/opera9.css' TYPE='text/css'>");
					  }
			} else {
 
				if (BrowserDetect.browser == "Safari"){
							 document.write("<LINK REL='stylesheet' HREF='../css/safari.css' TYPE='text/css'>");
				}else{
							 document.write("<LINK REL='stylesheet' HREF='../css/chrome.css' TYPE='text/css'>");
				}
			}
		}
	}
 
	</script> 
 

preg_match_all( '#(?<browser>' . join('|', array('msie', 'firefox', 'safari', 'webkit', 'opera', 'netscape', 'konqueror', 'gecko')).')[/ ]+(?<version>[0-9]+(?:\.[0-9]+)?)#', strtolower($_SERVER['HTTP_USER_AGENT']), $gear_browser);

function ObtenerNavegador($user_agent) {
     $navegadores = array(
          'Opera' => 'Opera',
          'Mozilla Firefox'=> '(Firebird)|(Firefox)',
          'Galeon' => 'Galeon',
          'Mozilla'=>'Gecko',
          'MyIE'=>'MyIE',
          'Lynx' => 'Lynx',
          'Netscape' => '(Mozilla/4\.75)|(Netscape6)|(Mozilla/4\.08)|(Mozilla/4\.5)|(Mozilla/4\.6)|(Mozilla/4\.79)',
          'Konqueror'=>'Konqueror',
          'Internet Explorer 7' => '(MSIE 7\.[0-9]+)',
          'Internet Explorer 6' => '(MSIE 6\.[0-9]+)',
          'Internet Explorer 5' => '(MSIE 5\.[0-9]+)',
          'Internet Explorer 4' => '(MSIE 4\.[0-9]+)',
);
foreach($navegadores as $navegador=>$pattern){
       if (eregi($pattern, $user_agent))
       return $navegador;
    }
return 'Desconocido';
}
?>
 
...
 
<?php echo ObtenerNavegador($_SERVER['HTTP_USER_AGENT']) ?>
 

 if (eregi($pattern, $user_agent))
 

$gear_browser = strtolower(trim($this -> gear_browser['browser'][0]));