[PHP知识库]php自动时间转换

/**
 * ('2021-11-11')->1636560000
 * (1636560000)->'2021-11-11 00:00:00'
 * (1636560000,'date')->'2021-11-11'
 * ('+1 day')->'2021-11-12 14:00:00'
 * ('+1 day','time')->'14:00:00'
 */
function now($st=null,$format=null){
	$f = $format=="date" ? "Y-m-d" : ($format=="time" ? "H:i:s" : "Y-m-d H:i:s");
	if(empty($st)){
		return date($f);
	}else if(is_numeric($st)){
		return date($f, $st);
	}else if(strtotime($st)!==false){
		if($format==null && preg_match('/[^0-9-:]/',str_replace(' ','',$st))==0){
			return strtotime($st);
		}else{
			return date($f, strtotime($st));
		}
	}else{
		return false;
	}
}