两个实用的函数

1，时间转化函数，将一个时间戳转化为n分钟前，n小时前...

function time_convert($time)
{
	$past_time = time() - $time;
	$str = '';
	if( 0<=$past_time && $past_time<60 )
	{
		$str = '刚刚';
	}else if(60<=$past_time && $past_time<60*60)
	{
		$str = round($past_time/60).'分钟前';
	}else if(60*60<=$past_time && $past_time<60*60*24)
	{
		$str = '约'.round($past_time/60/60).'小时前';
	}else if(60*60*24<=$past_time && $past_time<60*60*24*2)
	{
		$str = '昨天'.date('H:i',$time);
	}else if(60*60*24*2<=$past_time && $past_time<60*60*24*3)
	{
		$str = '前天'.date('H:i',$time);
	}else
	{
		if( intval(date('Y'))-intval(date('Y',$time))>0 )
			$str = date('Y-m-d H:i',$time);
		else
			$str = date('m-d H:i',$time);
	}
	
	return $str;
}

2,判断访问设备的类型，是移动设备还是电脑

function is_mobile_request()   
{   
  $_SERVER['ALL_HTTP'] = isset($_SERVER['ALL_HTTP']) ? $_SERVER['ALL_HTTP'] : '';   
  $mobile_browser = '0';   
  if(preg_match('/(up.browser|up.link|mmp|symbian|smartphone|midp|wap|phone|iphone|ipad|ipod|android|xoom)/i', strtolower($_SERVER['HTTP_USER_AGENT'])))   
	$mobile_browser++;   
  if((isset($_SERVER['HTTP_ACCEPT'])) and (strpos(strtolower($_SERVER['HTTP_ACCEPT']),'application/vnd.wap.xhtml+xml') !== false))   
	$mobile_browser++;   
  if(isset($_SERVER['HTTP_X_WAP_PROFILE']))   
	$mobile_browser++;   
  if(isset($_SERVER['HTTP_PROFILE']))   
	$mobile_browser++;   
  $mobile_ua = strtolower(substr($_SERVER['HTTP_USER_AGENT'],0,4));   
  $mobile_agents = array(   
		'w3c ','acs-','alav','alca','amoi','audi','avan','benq','bird','blac',   
		'blaz','brew','cell','cldc','cmd-','dang','doco','eric','hipt','inno',   
		'ipaq','java','jigs','kddi','keji','leno','lg-c','lg-d','lg-g','lge-',   
		'maui','maxo','midp','mits','mmef','mobi','mot-','moto','mwbp','nec-',   
		'newt','noki','oper','palm','pana','pant','phil','play','port','prox',   
		'qwap','sage','sams','sany','sch-','sec-','send','seri','sgh-','shar',   
		'sie-','siem','smal','smar','sony','sph-','symb','t-mo','teli','tim-',   
		'tosh','tsm-','upg1','upsi','vk-v','voda','wap-','wapa','wapi','wapp',   
		'wapr','webc','winw','winw','xda','xda-'  
		);   
  if(in_array($mobile_ua, $mobile_agents))   
	$mobile_browser++;   
  if(strpos(strtolower($_SERVER['ALL_HTTP']), 'operamini') !== false)   
	$mobile_browser++;   
  // Pre-final check to reset everything if the user is on Windows   
  if(strpos(strtolower($_SERVER['HTTP_USER_AGENT']), 'windows') !== false)   
	$mobile_browser=0;   
  // But WP7 is also Windows, with a slightly different characteristic   
  if(strpos(strtolower($_SERVER['HTTP_USER_AGENT']), 'windows phone') !== false)   
	$mobile_browser++;   
  if($mobile_browser>0)   
	return true;   
  else 
	return false;   
}