//缓存 Gravatar 头像
add_filter('get_avatar', 'fanly_cache_avatar');
function fanly_cache_avatar($avatar) {
	if(!is_dir('avatar'))//判断是否有缓存目录
		mkdir('avatar', 0755, true);//否者创建头像缓存目录
	$tmp = strpos($avatar, 'http');
	$g = substr($avatar, $tmp, strpos($avatar, "'", $tmp) - $tmp);
	$tmp = strpos($g, 'avatar/') + 7;
	$f = substr($g, $tmp, strpos($g, "?", $tmp) - $tmp);
	$w = home_url();
	list($width,$height,$type,$attr) = getimagesize($g);//获取头像参数
	$e = ABSPATH .'avatar/'. $f .'-'.$width.'.jpg';
	$t = 604800; //设定 7 天, 单位:秒
	if ( empty($default) ) $default = 'https://i.leiue.com/avatar.php';
	if ( !is_file($e) || (time() - filemtime($e)) > $t ){ //当头像不存在或者文件超过 7 天才更新
		copy(htmlspecialchars_decode($g), $e);
	}else{
		$avatar = strtr($avatar, array($g => $w.'/avatar/'.$f.'-'.$width.'.jpg'));
	}
	if (filesize($e) < 500) copy($default, $e);
	return $avatar;
}