What's the best to way to manage a singleton?

&Log::singleton($handler, $name, $ident, $conf, $maxLevel);

class Logger {

    private static $log;

    private function __construct() { }

    public static function init(Log $log) {
        self::$log = $log;
    }

    public static function get() {
        return self::$log;
    }

}

Logger::get()->doSomething($foo, $bar);

Logger::Write("Something happened");

private static $log = null;

public static function init(Log $log) {
    self::$log = $log;
}

public static function Write(String $str) {
    if($log == null)
        init(Log::singleton(...));

    $this->log->Write($str);
}