PHP获取当前时间的毫秒数

/*
         * 获取时间差，毫秒级
         */
        function get_subtraction()
        {
                $t1 = microtime(true);
                $t2 = microtime(true);
                return (($t2-$1)*1000).'ms';
        }

  /*
         * microsecond 微秒     millisecond 毫秒
         *返回时间戳的毫秒数部分
         */
        function get_millisecond()
        {
                list($usec, $sec) = explode(" ", microtime());
                $msec=round($usec*1000);
                return $msec;
                 
        }
         
        /*
         *
         *返回字符串的毫秒数时间戳
         */
        function get_total_millisecond()
        {
                $time = explode (" ", microtime () ); 
                $time = $time [1] . ($time [0] * 1000); 
                $time2 = explode ( ".", $time ); 
                $time = $time2 [0];
                return $time;
        }
    
        /*
         *
         *返回当前 Unix 时间戳和微秒数(用秒的小数表示)浮点数表示，常用来计算代码段执行时间
         */
         
        function microtime_float()
        {
            list($usec, $sec) = explode(" ", microtime());
            return ((float)$usec + (float)$sec);
        }