How to Replace Global Variable for MySQL Connection - php

Question

I came across an ancient PHP project where there's a modified QuickDB class(I had to strip it as it was too big for StackOverflow).
It'll work just fine if there's just one instance of QuickDB, but if you add another, it'll get real bad as the second instance overwrites the previous connection.
I'm struggling to find an elegant solution, could anyone give me a hint?
<?php
if (!function_exists("mysql_connect")) {
/* warning: fatal error "cannot redeclare" if a function was disabled in php.ini with disable_functions:
disable_functions =mysql_connect,mysql_pconnect,mysql_select_db,mysql_ping,mysql_query,mysql_fetch_assoc,mysql_num_rows,mysql_fetch_array,mysql_error,mysql_insert_id,mysql_close,mysql_real_escape_string,mysql_data_seek,mysql_result
*/
global $mysqli_connection;
function mysql_connect($host, $username, $password) {
global $mysqli_connection;
$mysqli_connection = mysqli_connect($host, $username, $password);
return $mysqli_connection;
}
function mysql_pconnect($host, $username, $password) {
return mysqli_connect("p:" . $host, $username, $password);
}
function mysql_num_fields($result) {
return mysqli_num_fields($result);
}
function mysql_field_name($result, $i) {
return mysqli_fetch_field_direct($result, $i)->name;
}
function mysql_fetch_object($result) {
return mysqli_fetch_object($result);
}
function mysql_select_db($db, $dbconnect = false) {
global $mysqli_connection;
if (!$dbconnect) {
$dbconnect = $mysqli_connection;
}
return mysqli_select_db($dbconnect, $db);
}
function mysql_ping($dbconnect = false) {
global $mysqli_connection;
if (!$dbconnect) {
$dbconnect = $mysqli_connection;
}
return mysqli_ping($dbconnect);
}
function mysql_query($stmt) {
global $mysqli_connection;
return mysqli_query($mysqli_connection, $stmt);
}
function mysql_fetch_assoc($erg) {
return mysqli_fetch_assoc($erg);
}
function mysql_num_rows($e) {
return mysqli_num_rows($e);
}
function mysql_affected_rows($e = NULL) {
return mysqli_affected_rows($e);
}
function mysql_fetch_array($e) {
return mysqli_fetch_array($e);
}
function mysql_error() {
global $mysqli_connection;
return mysqli_error($mysqli_connection);
}
function mysql_errorno() {
global $mysqli_connection;
return mysqli_errorno($mysqli_connection);
}
function mysql_insert_id() {
global $mysqli_connection;
return mysqli_insert_id($mysqli_connection);
}
function mysql_close() {
return true;
}
function mysql_fetch_row($erg) {
return mysqli_fetch_row($erg);
}
function mysql_errno() {
global $mysqli_connection;
return mysqli_errno($mysqli_connection);
}
function mysql_real_escape_string($s) {
global $mysqli_connection;
return mysqli_real_escape_string($mysqli_connection, $s);
}
function mysql_data_seek($re, $row) {
return mysqli_data_seek($re, $row);
}
function mysql_result($res, $row = 0, $col = 0) {
$numrows = mysqli_num_rows($res);
if ($numrows && $row <= ($numrows - 1) && $row >= 0) {
mysqli_data_seek($res, $row);
$resrow = (is_numeric($col)) ? mysqli_fetch_row($res) : mysqli_fetch_assoc($res);
if (isset($resrow[$col])) {
return $resrow[$col];
}
}
return false;
}
function mysql_set_charset($connection, $charset) {
return mysqli_set_charset($connection, $charset);
}
}
if (!function_exists('ereg_replace')) {
function ereg_replace($p1, $p2, $p3) {
return preg_replace("/".$p1.'/', $p2, $p3);
}
}
class QuickDB
{
private $con = null; // for db connection
private $row = null; // for fetched row
private $rows = null; // for number of rows fetched
private $affected = null; // for number of rows affected
private $insert_id = null; // for last inserted id
private $query = null; // for the last run query
public $show_errors = null; // for knowing whether to display errors
private $emsg = null; // for mysql error description
private $eno = null; // for mysql error number
// Intialize the class with connection to db
/**
* #param $host
* #param $user
* #param $password
* #param $db
* #param bool $persistent
* #param bool $show_errors
* #param bool $new_link
*/
public function __construct($host, $user, $password, $db, $persistent = false, $show_errors = false, $new_link = false)
{
if ($show_errors == true) {
$this->show_errors = true;
}
if ($persistent == true) {
$this->con = #mysql_pconnect($host, $user, $password, $new_link);
mysql_set_charset($this->con, "utf8"); // předefinování defaultu 8.6.2017
} else {
$this->con = #mysql_connect($host, $user, $password, $new_link);
mysql_set_charset($this->con, "utf8"); // předefinování defaultu 8.6.2017
}
if ($this->con) {
$result = mysql_select_db($db, $this->con) or die("Could Not Select The Database !!");
return $result;
} else {
die("Could Not Establish The Connection !!");
}
}
// Close the connection to database
/**
*
*/
public function __destruct()
{
$this->close();
}
// Close the connection to database
/**
* #return bool
*/
public function close()
{
//$result = #mysql_close($this->con); // orig
$result = #mysql_close($this->con);
return $result;
}
}