Call a method to connect to the DB with mysqli - php

Question

Hi i am trying to move from MySQL to MySQLi in my PHP script, i had this system class with the function that connects to the database that i call whenever i need, with a simple method like this:
Sys::database_connect();
the actual code of the function is:
function database_connect(){
require 'conf.php';//configuration file with database variables (sql_)
mysql_connect($sql_serv, $sql_user, $sql_pw) OR die('ERRO!!! não ligou a base de dados');
mysql_select_db($sql_bd);
}
after calling the function i can query the database without problem.
But I cant do the same with mysqli if I put this in the sys class:
function database_connect(){
require 'conf.php';
$mysqli = new mysqli($sql_serv, $sql_user, $sql_pw, $sql_bd);
if (mysqli_connect_errno()) {
printf("Ligação à Base de dados falhou: %s\n", mysqli_connect_error());
exit();
}
}
When I call
Sys::database_connect();
it connects to the database but i can't query has i used to what i would like would be a simple method as I have done with normal MySQL, if somebody can explain what am I doing wrong or why exactly I cannot do it like that...
Thank you in advance;
Fernando Andrade.

Answer 1

Your later queries have to use the mysqli connection identifier, you create when connecting to the database. So save this to a property of your system class and use it later on.
function database_connect(){
require 'conf.php';
$mysqli = new mysqli($sql_serv, $sql_user, $sql_pw, $sql_bd);
if (mysqli_connect_errno()) {
printf("Ligação à Base de dados falhou: %s\n", mysqli_connect_error());
exit();
}
Sys::$dbConn = $mysqli;
}
and then later on
function query( $sql ) {
Sys::$dbConn->query( $sql );
// error handling etc.
}

Answer 2

I wrote an extend for the mysqli database class
class database extends mysqli {
function __construct() {
parent::__construct('host', 'user', 'password', 'database');
if(mysqli_connect_error()) {
die('Connect error ('.mysqli_connect_errno().')'.mysqli_connect_error());
}
parent::query("SET NAMES 'utf8'");
}
function query($query) {
$result = parent::query($query);
if(!$result) {
echo "<strong>MySQL error</strong>: ".$this->error."<br />QUERY: ".$query;
die();
}
if(!is_object($result)) {
$result = new mysqli_result($this);
}
return $result;
}
}
So connecting to database is $db = new database()
Executing a query is $db->query(YOUR QUERY);