php mysql_query() problem

Question

phpstudy mysql connection successful
navicat mysql connection phpstudy mysql no problem
The table is
id username gender pass
1 bule man 111

php里
conn. php file:
Connect to phpstudy database:
Use $link= mysqli_connect(); there is no problem in verification after connection

dologin.php file:
Define the query statement after calling conn.php:
$sql="select * from yq ";

Execute the query statement:
$ result= mysqli_query($link,$sql);
Then something goes wrong.

Answer 1

Problems arise when dologin.php imports conn.php. Just connect to the database directly in dologin.php. This is the sentence to quote a file in the same directory, right? include_once("./conn.php");

Answer 2

Then I guess you didn’t specify it in your library.