extract browser detection regex into a constant

src/Monolog/Handler/ChromePHPHandler.php

@@ -32,6 +32,11 @@ class ChromePHPHandler extends AbstractProcessingHandler
      * Header name
      */
     const HEADER_NAME = 'X-ChromeLogger-Data';
+    
+    /**
+     * Regular expression to detect supported browsers (matches any Chrome, or Firefox 43+)
+     */
+    const USER_AGENT_REGEX = '{\b(?:Chrome/\d+(?:\.\d+)*|Firefox/(?:4[3-9]|[5-9]\d|\d{3,})(?:\.\d)*)\b}';
 
     protected static $initialized = false;
 
@@ -177,8 +182,7 @@ class ChromePHPHandler extends AbstractProcessingHandler
             return false;
         }
 
-        // matches any Chrome, or Firefox 43+
-        return preg_match('{\b(?:Chrome/\d+(?:\.\d+)*|Firefox/(?:4[3-9]|[5-9]\d|\d{3,})(?:\.\d)*)\b}', $_SERVER['HTTP_USER_AGENT']);
+        return preg_match(self::USER_AGENT_REGEX, $_SERVER['HTTP_USER_AGENT']);
     }
 
     /**