No error is reported for mysqli_connect, but notavalidMySQL-Linkresource is displayed in subsequent operations.

{Code...} reported an error: {code...} while using the object-oriented method is no problem. what is the problem?

$connect = mysqli_connect("host","user","password","db") or die("Error " . mysqli_error($connect));$result = mysql_query('select * from admin',$connnet);print(mysql_num_rows($result));mysql_close();

Error:

Warning: mysql_query(): supplied argument is not a valid MySQL-Link resourceWarning: mysql_num_rows(): supplied argument is not a valid MySQL result resourceWarning: mysql_close(): no MySQL-Link resource supplied

There is no problem with using the object-oriented method.
What is the problem?

Reply content:

$connect = mysqli_connect("host","user","password","db") or die("Error " . mysqli_error($connect));$result = mysql_query('select * from admin',$connnet);print(mysql_num_rows($result));mysql_close();

Error:

Warning: mysql_query(): supplied argument is not a valid MySQL-Link resourceWarning: mysql_num_rows(): supplied argument is not a valid MySQL result resourceWarning: mysql_close(): no MySQL-Link resource supplied

There is no problem with using the object-oriented method.
What is the problem?

Because you wrote the wrong letter...
The first variable is $ connect.
The second variable is $ connnect.
N More, okay?
Of course, you should also use mysqli_query instead of mysql_query.

Mysql_query-> mysqli_query
Mysql_num_rows-> mysqli_num_rows
Mysql_close-> mysqli_close

Dude, you have to use mysqli_xxx to use the connection created by mysqli_connect.
Mysqli_xxx and mysql_xxx cannot be mixed.