Is this PDO query okay to use in PHP OOP?

Question

Do you think this code is good if I want to do a simple SQL query? Is it safe to use? Or am I doing something wrong?

class DBconnection {
 private $dbusername = "testtest";
 private $dbpassword = "testtest";
 protected $conn;
 public function __construct(){
 try {
 $this->conn = new PDO("mysql:host=localhost;dbname=yxy_user;charset=utf8", $this->dbusername, $this->dbpassword);
 // set the PDO error mode to exception
 $this->conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
 } catch(PDOException $e) {
 echo "Connection failed: " . $e->getMessage();
 error_log("Failed to connect to database!", 0);
 }
 }
}
class Query extends DBconnection {
 
 public function FetchQuery($query, $params) { 
 $stmt = $this->conn->prepare($query);
 $stmt->execute($params);
 $result_query_fetch = $stmt->fetch(PDO::FETCH_ASSOC);
 if($result_query_fetch) {
 return $result_query_fetch;
 }
 else {
 return false;
 }
 }
 
 
}
$Query_Class = new Query;
$myResult = $Query_Class->FetchQuery("SELECT name 
 FROM customers 
 WHERE id =:id",
 array(":id" => "12345"));
if($myResult){
 print_r ($myResult);
}
else {
 echo "No results!";
}

• BCdotWEB: The current question title, which states your concerns about the code, applies to too many questions on this site to be useful. The site standard is for the title to simply state the task accomplished by the code. Please see How do I ask a good question?.

Answer 1

Nope, this "PDO query" is NOT okay, especially "to use in PHP OOP".

The Database class does nothing useful, and shouldn't exist.
The Query class should never extend the Database class, because a query is not a database.
The code at whole is just an attempt to create a single procedure FetchQuery() - so you have to do exactly that:

db_credentials.php

<?php
$dbhost = 'localhost';
$dbname = 'yxy_user';
$dbusername = '';
$dbpassword = '';

db.php

<?php
require 'db_credentials.php';
$pdo = new PDO("mysql:host=$dbhost;dbname=$dbname;charset=utf8mb4", $dbusername, $dbpassword);
// set the PDO error mode to exception
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
function pdo($pdo, $sql, $args = NULL)
{
 $stmt = $pdo->prepare($sql);
 $stmt->execute($args);
 return $stmt;
}

and then use it elsewhere

<?php
require 'db.php';
$sql = "SELECT name FROM customers WHERE id =:id";
$myResult = pdo($sql,[":id" => "12345"])->fetch(PDO::FETCH_ASSOC);
if($myResult){
 print_r ($myResult);
}
else {
 echo "No results!";
}

Note that this function returns the PDOStatement instance, which makes it extremely convenient and universal, you can see usage examples in this answer.

As of OOP, it is not an easy topic. There is a lot to learn. But above all, there must be a clear purpose for the class. For the moment I just don't see any use for the classes provided. But if you have other ideas or use cases for your database classes, you can post another question.