original_string: public static function os()
      {
          if ( is_null( self::$os ) )
          {
              $uname = php_uname( 's' );
              if ( substr( $uname, 0, 7 ) == 'Windows' )
              {
                  self::$os = 'Windows';
              }
              elseif ( substr( $uname, 0, 3 ) == 'Mac' )
              {
                  self::$os = 'Mac';
              }
              elseif ( strtolower( $uname ) == 'linux' )
              {
                  self::$os = 'Linux';
              }
              elseif ( strtolower( substr( $uname, 0, 7 ) ) == 'freebsd' )
              {
                  self::$os = 'FreeBSD';
              }
              else
              {
                  self::$os = PHP_OS;
              }
          }
          return self::$os;
      }
code: public static function os()
      {
          if ( is_null( self::$os ) )
          {
              $uname = php_uname( 's' );
              if ( substr( $uname, 0, 7 ) == 'Windows' )
              {
                  self::$os = 'Windows';
              }
              elseif ( substr( $uname, 0, 3 ) == 'Mac' )
              {
                  self::$os = 'Mac';
              }
              elseif ( strtolower( $uname ) == 'linux' )
              {
                  self::$os = 'Linux';
              }
              elseif ( strtolower( substr( $uname, 0, 7 ) ) == 'freebsd' )
              {
                  self::$os = 'FreeBSD';
              }
              else
              {
                  self::$os = PHP_OS;
              }
          }
          return self::$os;
      }
code_tokens: public static function os ( ) { if ( is_null ( self :: $ os ) ) { $ uname = php_uname ( 's' ) ; if ( substr ( $ uname , 0 , 7 ) == 'Windows' ) { self :: $ os = 'Windows' ; } elseif ( substr ( $ uname , 0 , 3 ) == 'Mac' ) { self :: $ os = 'Mac' ; } elseif ( strtolower ( $ uname ) == 'linux' ) { self :: $ os = 'Linux' ; } elseif ( strtolower ( substr ( $ uname , 0 , 7 ) ) == 'freebsd' ) { self :: $ os = 'FreeBSD' ; } else { self :: $ os = PHP_OS ; } } return self :: $ os ; }
docstring: Returns the operating system on which PHP is running.
  
  This method returns a sanitized form of the OS name, example
  return values are "Windows", "Mac", "Linux" and "FreeBSD". In
  all other cases it returns the value of the internal PHP constant
  PHP_OS.
  
  @return string
docstring_tokens: Returns the operating system on which PHP is running .