Php uses the mysqli module to connect to the database Fatalerror: Calltoamemberfunctionquery (). Solution

Php uses the mysqli module to connect to the database Fatalerror: Calltoamemberfunctionquery ().... This error occurs: Fatalerror: Calltoamemberfunctionquery () onanon-php using the mysqli module to connect to the database Fatal error: Call to a member function query ()....
This error occurs: Fatal error: Call to a member function query () on a non-object in D: \ wamp \ www \ bills \ model \ UserDB. class. php on line 24
The code is as follows:

PHP code

  
  Mysqli = new mysqli ($ dbhost, $ dbuser, $ dbpwd, $ dbname); if (mysqli_connect_errno () {echo "an error occurred while connecting to the item database! ";}} Public function close () {if ($ this-> mysqli) $ this-> mysqli-> close (); $ this-> mysqli = FALSE ;} public function _ destruct () {$ this-> close () ;}} class UserDB extends Database {public function queryUserByName ($ name) {$ query = "SELECT * FROM Users WHERE name = '". $ name. "'"; if ($ result = $ this-> mysqli-> query ($ query) // An error is prompted here !! Return true; else return false ;}

Then, the above class object is called on another page:

PHP code

  
  QueryUserByName ($ lvalue ["name"]); echo "alert"; if ($ rtmp) // This name is not registered {$ rusers = new User ($ lvalue ); if ($ udb-> addUser ($ rusers) {setcookie ("start", 0); setcookie ("userInfo", serialize ($ rusers )); setcookie ("username", $ rusers-> name); header ("Location :.. /view/index. php ");} else header (" Location :.. /view/errors. php? Value = tianjia ");} break ;}

------ Solution --------------------
Public function _ construct ($ configFile = "config. inc. php") // Two underlines