diff --git a/mobile_theme.module b/mobile_theme.module
index e94585a..6fe766d 100644
--- a/mobile_theme.module
+++ b/mobile_theme.module
@@ -103,31 +103,33 @@ function mobile_theme_detect_getbrowser() {
  */
 function mobile_theme_detect_php() {
   $mobile_browser = 0;
-  if (preg_match('/(up.browser|up.link|mmp|symbian|smartphone|midp|wap|phone|android)/i', strtolower($_SERVER['HTTP_USER_AGENT']))) {
-    $mobile_browser++;
-  }
-  if ((strpos(strtolower($_SERVER['HTTP_ACCEPT']),'application/vnd.wap.xhtml+xml') > 0) or ((isset($_SERVER['HTTP_X_WAP_PROFILE']) or isset($_SERVER['HTTP_PROFILE'])))) {
-    $mobile_browser++;
-  }
-  $mobile_ua = strtolower(substr($_SERVER['HTTP_USER_AGENT'], 0, 4));
-  $mobile_agents = array(
-      'w3c ','acs-','alav','alca','amoi','audi','avan','benq','bird','blac',
-      'blaz','brew','cell','cldc','cmd-','dang','doco','eric','hipt','inno',
-      'ipaq','java','jigs','kddi','keji','leno','lg-c','lg-d','lg-g','lge-',
-      'maui','maxo','midp','mits','mmef','mobi','mot-','moto','mwbp','nec-',
-      'newt','noki','oper','palm','pana','pant','phil','play','port','prox',
-      'qwap','sage','sams','sany','sch-','sec-','send','seri','sgh-','shar',
-      'sie-','siem','smal','smar','sony','sph-','symb','t-mo','teli','tim-',
-      'tosh','tsm-','upg1','upsi','vk-v','voda','wap-','wapa','wapi','wapp',
-      'wapr','webc','winw','winw','xda ','xda-');
-  if (in_array($mobile_ua,$mobile_agents)) {
-    $mobile_browser++;
-  }
-  if (isset($_SERVER['ALL_HTTP']) && strpos(strtolower($_SERVER['ALL_HTTP']), 'OperaMini') > 0) {
-    $mobile_browser++;
-  }
-  if (strpos(strtolower($_SERVER['HTTP_USER_AGENT']), 'windows') > 0) {
-    $mobile_browser = 0;
+  if (isset($_SERVER['HTTP_USER_AGENT'])) {
+	if (preg_match('/(up.browser|up.link|mmp|symbian|smartphone|midp|wap|phone|android)/i', strtolower($_SERVER['HTTP_USER_AGENT']))) {
+		$mobile_browser++;
+	}
+	if (isset($_SERVER['HTTP_ACCEPT']) and ((strpos(strtolower($_SERVER['HTTP_ACCEPT']),'application/vnd.wap.xhtml+xml') > 0) or ((isset($_SERVER['HTTP_X_WAP_PROFILE']) or isset($_SERVER['HTTP_PROFILE']))))) {
+		$mobile_browser++;
+	}
+	$mobile_ua = strtolower(substr($_SERVER['HTTP_USER_AGENT'], 0, 4));
+	$mobile_agents = array(
+		'w3c ','acs-','alav','alca','amoi','audi','avan','benq','bird','blac',
+		'blaz','brew','cell','cldc','cmd-','dang','doco','eric','hipt','inno',
+		'ipaq','java','jigs','kddi','keji','leno','lg-c','lg-d','lg-g','lge-',
+		'maui','maxo','midp','mits','mmef','mobi','mot-','moto','mwbp','nec-',
+		'newt','noki','oper','palm','pana','pant','phil','play','port','prox',
+		'qwap','sage','sams','sany','sch-','sec-','send','seri','sgh-','shar',
+		'sie-','siem','smal','smar','sony','sph-','symb','t-mo','teli','tim-',
+		'tosh','tsm-','upg1','upsi','vk-v','voda','wap-','wapa','wapi','wapp',
+		'wapr','webc','winw','winw','xda ','xda-');
+	if (in_array($mobile_ua,$mobile_agents)) {
+		$mobile_browser++;
+	}
+	if (isset($_SERVER['ALL_HTTP']) && strpos(strtolower($_SERVER['ALL_HTTP']), 'OperaMini') > 0) {
+		$mobile_browser++;
+	}
+	if (strpos(strtolower($_SERVER['HTTP_USER_AGENT']), 'windows') > 0) {
+		$mobile_browser = 0;
+	}
   }
   return $mobile_browser > 0; 
 }