去掉字符串最后一个逗号，并按逗号分隔插入数据

$data = $this->request->param();//$data='1,2,3,4,'
$plist=rtrim($data['plist'], ",");//$plist='1,2,3,4'

$str=explode(",",$plist); //$str为以逗号为分隔的数组

foreach ($str as $key => $val) { 
model('Imgfile')->insert(['url'=>json_encode($val)]); //tp5的sql语句
}