PDO throw error Undefined variable: pdo in - php

Question

I have 3 files: dbconnect (here's declaration of $pdo), core.php (file with class to manage) and test.php.
I want to receive data from DB, but I have error:
Notice: Undefined variable: pdo in C:\xampp\htdocs\project\core.php on line 24
In dbconnect $pdo is in try catch, but before this I put: $pdo=null(to make variable accessible) but it doesn't work.
dbconnect ---> core.php(error here) ---> test.php;
//dbconnect.php
<?php
$mysql_host = 'localhost';
$username = 'root';
$password = '';
$database = 'db';
$pdo = null;
try {
$pdo = new PDO('mysql:host='.$mysql_host.';dbname='.$database.';charset=utf8', $username, $password );
}
catch(PDOException $e) {
echo 'Połączenie nie mogło zostać utworzone.<br />';
}
?>
//core.php
require_once('cms/dbconnect.php');
class getCore{
public $link_allegro;
public $link_facebook;
function getLinks(){
$query= $pdo->query('SELECT `url` FROM `links` WHERE `title` = "facebook"');
$row = $query->fetch();
$this->link_facebook = $row["url"];
$query= $pdo->query('SELECT url FROM links WHERE title = "allegro"');
$row = $query->fetch();
$this->link_allegro = $row["url"];
$query->closeCursor();
}
}
//test.php
<?php
require_once('core.php');
$tmp = new getCore;
$tmp->getLinks();
echo $tmp->link_allegro;
echo $tmp->link_facebook;
?>
Anyone can solve this? Thanks.

Answer 1

This is a scoping problem. $pdo doesn't exists in your getCore class.
You can make a DatabaseConnect class to manage your db access.
You can use this basic class for your database connection :
<?php
class DatabaseConnect {
private $mysql_host = 'localhost';
private $username = 'root';
private $password = '';
private $database = 'db';
private $pdo = null;
public function getPdo(){
return $this->pdo;
}
public function __construct(){
try {
$this->pdo = new PDO('mysql:host='.$mysql_host.';dbname='.$database.';charset=utf8', $username, $password );
}
catch(PDOException $e) {
echo 'Połączenie nie mogło zostać utworzone.<br />';
}
}
}
?>
You can getting your PDO instance in an other class with calling DatabaseConnect object -> getPdo() :
- Instannciate a new DatabaseConnect.
- Get PDO instance with the methof of the class.
Like that :
$databaseConnect = new DatabaseConnect();
$pdo = $databaseConnect->getPdo();
You next code :
//core.php
require_once('cms/dbconnect.php');
class getCore{
public $link_allegro;
public $link_facebook;
function getLinks(){
$databaseConnect = new DatabaseConnect();
$pdo = $databaseConnect-getPdo();
$query= $pdo->query('SELECT `url` FROM `links` WHERE `title` = "facebook"');
$row = $query->fetch();
$this->link_facebook = $row["url"];
$query= $pdo->query('SELECT url FROM links WHERE title = "allegro"');
$row = $query->fetch();
$this->link_allegro = $row["url"];
$query->closeCursor();
}
}
//test.php
<?php
require_once('core.php');
$tmp = new getCore;
$tmp->getLinks();
echo $tmp->link_allegro;
echo $tmp->link_facebook;

Answer 2

You need to pass $pdo to the getLinks() function as an input to make it available for use. you could try getLinks($pdo)