Difference between 2 PHP pdo classes?

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Hi,

Is anyone around, to give some information in regards to the difference between the two queries, pdo connection class and which is better and why?

What I have tried:

PDO Database Connection Class 1

class DB extends PDO {

    protected $db_name = "yog";
    protected $db_user = "root";
    protected $db_pass = "";
    protected $db_host = "localhost";

    public function __construct() {
        try {
            parent::__construct("mysql:host={$this->db_host};dbname={$this->db_name}", $this->db_user, $this->db_pass);
        } catch (PDOException $e) {
            echo $e->getMessage();
        }
    }

PDO Database Connection Class 2

class DB {

    private $dbHost     = "localhost";
    private $dbUsername = "root";
    private $dbPassword = "";
    private $dbName     = "yog";

    public function __construct(){
        if(!isset($this->db)){
            // Connect to the database
            try{
                $conn = new PDO("mysql:host=".$this->dbHost.";dbname=".$this->dbName, $this->dbUsername, $this->dbPassword);
                $conn -> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
                $this->db = $conn;
            }catch(PDOException $e){
                die("Failed to connect with MySQL: " . $e->getMessage());
            }
        }
    }

Posted 9-Jan-19 10:30am

Member 14093672

Updated 9-Jan-19 15:30pm

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Mohibur Rashid 9-Jan-19 17:46pm

I would suggest you not to use the second function. Since you are extending PDO, you should not write the connection function. It's look like in second function you are pointing to connect through this object, better is not to do this, rather use the first function and extend your other required functions

Member 14093672 9-Jan-19 19:39pm

Hi Mohibur AS Salam O ALykum, please kindly give some explanation and why we cannot use it in simple terms please. Jazakallah Khair

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Mohibur Rashid · Answer 1 · 2019-01-09T15:25:00

Walaikum Salam.

It seems, you have removed extension from the second class. Now Second class look ok.

Which one you will use depends on your approach.
But second class has a variable $db; which is not private. Can be modified out side of the class, and at the beginning of the class you are checking whether $this->db exists or not; in construction $this->db does not exists anyway;

PHP

<?php
class cc {
  public function __construct() {
    $this->a = 10;
    $this->b = 20;
  }
}

$x= new cc();
print_r($x);

Result:

cc Object
(
    [a] => 10
    [b] => 20
)

Which mean it works; but not a good practice. Will lead to unexpected disaster.

Your first class,

$db = new DB();
$res = $db->query("The Query");

This has great advantage. It will let you directly access any function of PDO Class without any restriction. This is useful, when working as team. You still can add functions to do additional job. And you can wrap existing function of PDO if you have to.

On the other hand, with second class, you will have to implement many functions to access individual function, this is going to be problematic in the long run.

So, I will still suggest you to use the first class.

SQL

-------------ADDITIONAL-------------

About the question you have asked related to set attribute:

class DB extends PDO {
...
...
}

$conn = new DB();
conn->setAttribute(PDO::CONSTANT, PDO::CONSTANT); <-- this will solve your attribute setting issue. Please, take your time to understand how class, extended class  works. 

// This should work too
$conn->setAttribute(DB::CONSTANT, DB::CONSTANT);

You should not open more than one connection in a single http request, you need to find a way to let the connection float around in the entire request and make sure that connection closed at the end of request.