PHP“.=”的作用

$test .= "123";
$test .="456";
echo $test //输出123456

使用".="和mysqli_multi_query()批量插入数据

$sql="insert into user (username,password,phone) values (admin,123456,133333345);";
$sql.="insert into user (username,password,phone) values (admin1,12345678,13482757235);";
$sql .="insert into user (username,passowrd,phone) values (admin2,142356287,32748658465);";
if($con->mysqli_multi_query()==TRUE){
echo "插入成功";
}else{
echo"插入失败";
}