Cannot fetch record using PHP and MySQL - php

Question

I am unable to fetch record from a MySQL database using PHP. Here is my code.
user.php:
require_once ('../../include/dbconfig.php');
require_once ('common.php');
error_reporting(E_ALL);
ini_set('display_errors', '1');
$userClass=new CommonConnectorFuncs();
$redata=$userClass->insertUserRecordForSignup();
echo $redata;exit;
common.php:
require_once ('../../include/dbconfig.php');
error_reporting(E_ALL);
ini_set('display_errors', '1');
$protocol = (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] != "off") ? "https" : "http";
$imagepath=$protocol. "://" . $_SERVER['HTTP_HOST']."/connector/upload/";
class CommonConnectorFuncs{
function __construct() {
}
// destructor
function __destruct() {
// $this->close();
}
public function insertUserRecordForSignup(){
$sql=mysqli_query($connect,"select * from cn_user_info order by user_id desc");
while ($row=mysqli_fetch_array($sql)) {
$data[]=$row;
}
return $data;
}
}
Here I am trying to fetch record and print through class but it's throwing the below message.
Notice: Undefined variable: connect in common.php on line 16
Warning: mysqli_query() expects parameter 1 to be mysqli, null given in common.php on line 16
Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, null given in common.php on line 17
Notice: Undefined variable: data in common.php on line 20
Those query is working fine inside the user.php file but it's not working in common.php file.

Answer 1

As mentioned in comments, this is a scoping issue. Specifically, $connect is not in scope.
Notice: Undefined variable: connect in common.php on line 16
where connect is not defined anywhere.
Moreover, It's exactly as the error states as you're passing arguments to mysqli_query incorrectly. Assumming $connect is your mysqli connection generated at some point by new mysqli() it should be:
$sql = "select * from cn_user_info order by user_id desc";
$result = mysqli_query( $connect,$sql) or die('Could not look up user information; ' . mysqli_error($connect))
Hope it helps!

Answer 2

Make the connect variable a property of your class as by parsing it in your construct function
require_once ('../../include/dbconfig.php');
require_once ('common.php');
error_reporting(E_ALL);
ini_set('display_errors', '1');
$userClass=new CommonConnectorFuncs($connect);
$redata=$userClass->insertUserRecordForSignup();
echo $redata;exit;
In your class,
class CommonConnectorFuncs{
var $Connection;
function __construct($connection) {
try{
if($connection != null){
$this->Connection = $connection;
}else{
throw new Exception('Connection is null. COuld not process further');
}
}catch(Exception $ex){
echo $ex->getMessage();
exit;
}
}
// destructor
function __destruct() {
// $this->close();
}
public function insertUserRecordForSignup(){
$sql=mysqli_query($this->Connection,"select * from cn_user_info order by user_id desc");
while ($row=mysqli_fetch_array($sql)) {
$data[]=$row;
}
return $data;
}
}

Answer 3

The problem is in that you are trying to access a global variable within a function.
First of all, make sure you include the php file with the relevant database connection. And as you are trying to access a global variable there are two ways to achieve this.
Method 1
Create a global variable at the top of the function.
global $connect;
But as Qirel says in this comment, it is a bad practise, so I'd suggest the next.
Method 2
Pass the connection to the function's parameters.
public function insertUserRecordForSignup($connect){
$sql=mysqli_query($connect,"select * from cn_user_info order by user_id desc");
while ($row=mysqli_fetch_array($sql)) {
$data[]=$row;
}
return $data;
}
Hope you find this useful.