class undefined property in php - php

Question

maybe this is a possible duplicate, i have search here some questions like this but i have tried all the answers, but i still got this error
Notice: Undefined property: User::$_pdo in D:\xampp\htdocs\pengun\classes\DB.php on line 32
and this error
Fatal error: Call to a member function prepare() on a non-object in D:\xampp\htdocs\pengun\classes\DB.php on line 32
this is my DB class
<?php
class DB {
private $_pdo, $_query, $_result, $_count, $_row;
public function __construct($host, $dbname, $user, $password) {
$this->host = $host;
$this->user = $user;
$this->password = $password;
$this->dbname = $dbname;
try {
$_pdo = new PDO('mysql:host=' . $this->host . ';dbname=' . $this->dbname, $this->user, $this->password);
} catch (PDOException $e) {
die($e->getMessage());
}
$_pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
public function select($fields, $table, $where = array()) {
if(count($where) === 3) {
$operators = array('=','>','<','>=','<=');
$column = $where[0];
$operator = $where[1];
$value = $where[2];
if(in_array($operator, $operators)) {
$sql = "SELECT {$fields} FROM {$table} WHERE {$column} {$operator} {$value}";
if($this->_query = $this->_pdo->prepare($sql)) {
$this->_query->execute();
$this->_row = $this->_query->fetch();
print_r($this->_row);
}
}
}
}
}
can someone please tell me what is the problem with my code? thanks in advance.

Answer 1

Because in constructor, you are assigning new PDO just to local variable accessible only inside constructor. You have to use:
$this->_pdo = new PDO('mysql:host=' . $this->host . ';dbname=' . $this->dbname, $this->user, $this->password);
...
$this->_pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

Answer 2

You are assigned PDO object to local variable in constructor. You must set class variable!
Change
$_pdo
to
$this->_pdo
in lines 13 and 18.