<?php

header("Content-type: text/html; charset=utf-8");

$txDate = '2016-06-16';

$dateTime = explode('-', $txDate);

$Time = $dateTime[0].$dateTime[1].$dateTime[2];

var_dump($Time);

结果：string '20160616' (length=8)

?>

 $dateTime = explode('-', $params['txDate']);
 $dateTime = $dateTime['0'].$dateTime['1'].$dateTime['2'];　　　var_dump($dateTime); //20160616

<?php

header("Content-type: text/html; charset=utf-8");

$txDate = '2016-06-16';

$dateTime1 = strtotime($txDate);  //int 1466028000 将英文文本日期时间解析为 Unix 时间戳：

$dateTime2= date("Y-m-d H:i:s",$dateTime1); //string '2016-06-16 00:00:00' (length=19)  Date() 函数把时间戳格式化为更易读的日期和时间。

//拼接今日最后时间2016-06-16 23:59:59

$dateTime= date("Y-m-d H:i:s",strtotime(date("Y-m-d",strtotime($dateTime2))."+ 23 hours 59 minutes  59 seconds ")); //string '2016-06-16 23:59:59' (length=19)

$sql = select * form `vvt_user` where userid = 100 AND date_time >= $dateTime2 AND date_time <= $dateTime;

?>

$sql .=   ' AND UNIX_TIMESTAMP(vvt_repayment.date) >= '.strtotime($day);

$sql .=   ' AND UNIX_TIMESTAMP(vvt_repayment.date) <= '.strtotime($endday);