list($usec, $sec) = explode(' ', microtime());

$usec2msec = $usec * 1000;    //计算微秒部分的毫秒数(微秒部分并不是微秒,这部分的单位是秒)
$sec2msec = $sec * 1000;    //计算秒部分的毫秒数
$usec2msec2float = (float)$usec2msec;    
$sec2msec2float = (float)$sec2msec;    
$msec = $usec2msec2float + $sec2msec2float; //加起来就对了

echo $usec,'<br>';
echo $usec2msec,'<br>------------<br>';
echo $sec,'<br>';
echo $sec2msec,'<br>------------<br>';
echo $usec2msec2float,'<br>';
echo $sec2msec2float,'<br>------------<br>';
echo $msec,'<br>';
echo time(),'<br>';

$arrMsc = explode('.', $msec);
var_dump($arrMsc[0]);exit;

1 list($usec, $sec) = explode(' ', microtime());
2 
3         $usec2msec = $usec * 1000;  //计算微秒部分的毫秒数(微秒部分并不是微秒,这部分的单位是秒)
4         $usec2msec2int = intval($usec2msec);
5         $sec2msec = $sec * 1000;    //计算秒部分的毫秒数
6         $sec2msec2int = intval($sec2msec);
7         
8         $msec = $sec2msec2int + $usec2msec2int; //加起来就对了
9         var_dump($msec);