PDO抛出错误未定义的变量：pdo in

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;