用户代理可以被伪造，最好不要依赖用户代理字符串，如果您只想检测方向，则可以使用 CSS3 媒体查询（您可以探索著名的响应式框架引导程序的 CSS 以检查如何处理使用 CSS 的方向部分）
这是小CSS：
@media only screen and (max-width: 999px) {
/* rules that only apply for canvases narrower than 1000px */
}
@media only screen and (device-width: 768px) and (orientation: landscape) {
/* rules for iPad in landscape orientation */
}
@media only screen and (min-device-width: 320px) and (max-device-width: 480px) {
/* iPhone, Android rules here */
}
阅读更多：关于 CSS 方向检测
或者您可以使用 JavaScript 找到方向：
// Listen for orientation changes
window.addEventListener("orientationchange", function() {
// Announce the new orientation number
alert(window.orientation);
}, false);
阅读更多：关于使用 JS 检测方向
最后，如果您真的想使用用户代理字符串，那么这段代码将对您有很大帮助，几乎在每个浏览器上都能正常工作：
<?php
class BrowserDetection {
private $_user_agent;
private $_name;
private $_version;
private $_platform;
private $_basic_browser = array (
'Trident\/7.0' => 'Internet Explorer 11',
'Beamrise' => 'Beamrise',
'Opera' => 'Opera',
'OPR' => 'Opera',
'Shiira' => 'Shiira',
'Chimera' => 'Chimera',
'Phoenix' => 'Phoenix',
'Firebird' => 'Firebird',
'Camino' => 'Camino',
'Netscape' => 'Netscape',
'OmniWeb' => 'OmniWeb',
'Konqueror' => 'Konqueror',
'icab' => 'iCab',
'Lynx' => 'Lynx',
'Links' => 'Links',
'hotjava' => 'HotJava',
'amaya' => 'Amaya',
'IBrowse' => 'IBrowse',
'iTunes' => 'iTunes',
'Silk' => 'Silk',
'Dillo' => 'Dillo',
'Maxthon' => 'Maxthon',
'Arora' => 'Arora',
'Galeon' => 'Galeon',
'Iceape' => 'Iceape',
'Iceweasel' => 'Iceweasel',
'Midori' => 'Midori',
'QupZilla' => 'QupZilla',
'Namoroka' => 'Namoroka',
'NetSurf' => 'NetSurf',
'BOLT' => 'BOLT',
'EudoraWeb' => 'EudoraWeb',
'shadowfox' => 'ShadowFox',
'Swiftfox' => 'Swiftfox',
'Uzbl' => 'Uzbl',
'UCBrowser' => 'UCBrowser',
'Kindle' => 'Kindle',
'wOSBrowser' => 'wOSBrowser',
'Epiphany' => 'Epiphany',
'SeaMonkey' => 'SeaMonkey',
'Avant Browser' => 'Avant Browser',
'Firefox' => 'Firefox',
'Chrome' => 'Google Chrome',
'MSIE' => 'Internet Explorer',
'Internet Explorer' => 'Internet Explorer',
'Safari' => 'Safari',
'Mozilla' => 'Mozilla'
);
private $_basic_platform = array(
'windows' => 'Windows',
'iPad' => 'iPad',
'iPod' => 'iPod',
'iPhone' => 'iPhone',
'mac' => 'Apple',
'android' => 'Android',
'linux' => 'Linux',
'Nokia' => 'Nokia',
'BlackBerry' => 'BlackBerry',
'FreeBSD' => 'FreeBSD',
'OpenBSD' => 'OpenBSD',
'NetBSD' => 'NetBSD',
'UNIX' => 'UNIX',
'DragonFly' => 'DragonFlyBSD',
'OpenSolaris' => 'OpenSolaris',
'SunOS' => 'SunOS',
'OS\/2' => 'OS/2',
'BeOS' => 'BeOS',
'win' => 'Windows',
'Dillo' => 'Linux',
'PalmOS' => 'PalmOS',
'RebelMouse' => 'RebelMouse'
);
function __construct($ua = '') {
if(empty($ua)) {
$this->_user_agent = (!empty($_SERVER['HTTP_USER_AGENT'])?$_SERVER['HTTP_USER_AGENT']:getenv('HTTP_USER_AGENT'));
}
else {
$this->_user_agent = $ua;
}
}
function detect() {
$this->detectBrowser();
$this->detectPlatform();
return $this;
}
function detectBrowser() {
foreach($this->_basic_browser as $pattern => $name) {
if( preg_match("/".$pattern."/i",$this->_user_agent, $match)) {
$this->_name = $name;
// finally get the correct version number
$known = array('Version', $pattern, 'other');
$pattern_version = '#(?<browser>' . join('|', $known).')[/ ]+(?<version>[0-9.|a-zA-Z.]*)#';
if (!preg_match_all($pattern_version, $this->_user_agent, $matches)) {
// we have no matching number just continue
}
// see how many we have
$i = count($matches['browser']);
if ($i != 1) {
//we will have two since we are not using 'other' argument yet
//see if version is before or after the name
if (strripos($this->_user_agent,"Version") < strripos($this->_user_agent,$pattern)){
@$this->_version = $matches['version'][0];
}
else {
@$this->_version = $matches['version'][1];
}
}
else {
$this->_version = $matches['version'][0];
}
break;
}
}
}
function detectPlatform() {
foreach($this->_basic_platform as $key => $platform) {
if (stripos($this->_user_agent, $key) !== false) {
$this->_platform = $platform;
break;
}
}
}
function getBrowser() {
if(!empty($this->_name)) {
return $this->_name;
}
}
function getVersion() {
return $this->_version;
}
function getPlatform() {
if(!empty($this->_platform)) {
return $this->_platform;
}
}
function getUserAgent() {
return $this->_user_agent;
}
function getInfo() {
return "<strong>Browser Name:</strong> {$this->getBrowser()}<br/>\n" .
"<strong>Browser Version:</strong> {$this->getVersion()}<br/>\n" .
"<strong>Browser User Agent String:</strong> {$this->getUserAgent()}<br/>\n" .
"<strong>Platform:</strong> {$this->getPlatform()}<br/>";
}
}
$obj = new BrowserDetection();
echo $obj->detect()->getInfo();
上面的代码几乎适用于所有浏览器，我希望它对你有所帮助。