PHP多个连续空格回车替换为一个，怎么写更简短

function re($content)
{
    /* return preg_replace('/(){3,}|( ){3,}/i'),'\\1',$content); */ //错误！
    /* return preg_replace('/(| ){3,}/i'),'\\1',$content); */ //错误！
    return preg_replace(array('/(){3,}/i','/( ){3,}/i'),'\\1',$content);
}


//test
$content = '1111    



@@@



aaaaM

';
echo re($content);
exit();