mysqli_connect does not report an error, but subsequent operations show not a valid MySQL-Link resource.

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

Error report:

<code>Warning: mysql_query(): supplied argument is not a valid MySQL-Link resource
Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource
Warning: mysql_close(): no MySQL-Link resource supplied
</code>

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

Reply content:

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

Error report:

<code>Warning: mysql_query(): supplied argument is not a valid MySQL-Link resource
Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource
Warning: mysql_close(): no MySQL-Link resource supplied
</code>

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

Because you wrote the wrong letters...
The first variable is $connect
The second variable is $connnect
There is an extra n, okay?
Of course, use mysqli_query instead of mysql_query

mysql_query -> mysqli_query
mysql_num_rows -> mysqli_num_rows
mysql_close -> mysqli_close

Brother, the connection you create with mysqli_connect must be used with mysqli_xxx
mysqli_xxx and mysql_xxx cannot be mixed