How to use database connection in other classes

Question

PHP programming is pretty new to me - so I hope that I don't ask something stupid. However, I could not find any answer to my problem :-(

I have saved my database connection in a separate .php file. Let's say "connection.inc.php"

connection.inc.php looks as follows:

$host   = "name.server.com";
$dbname = "foo";
$user   = "bar";
$pass   = "PaSW0rd";

try
{
    $DBH = new PDO("mysql:host=$host;dbname=$dbname",$user,$pass,
    array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));

}
catch(PDOException $e)
{
   ...
}

In my index.php I would include the connection.inc.php with 'include_once "connection.inc.php"

Additionally, I have a class called house.class.php in which I have a method with an SQL query to my database. I call the method via 'getColor($id, $DBH)' from my index.php

Is there any way to use the method without always putting $DBH into the call?

Thanks for your help!

You can get $DBH from inside the function itself. Or you can get $DGH in the constructor of the class. — coderodour, Apr 24 '17 at 18:35
How do I get $DBH from inside the function itself? What do I have to do? This might be the answer to my question. Thx — Tobi, Apr 24 '17 at 18:55
It's better to inject it into the house class constructor and assign it as the object property/field. — frz3993, Apr 24 '17 at 19:03

score 0 · Answer 1 · answered Apr 24 '17 at 19:10

You should get the $DBH from the class itself rather than in the index file. Then you can have that instance of the database connection available to use class wide with other methofs in that class as well without having to re-connect for every function or having to provide every function the connection as an argument.

An example of this would look something like this:

house.class.php

<?php
  class House{

      private $DBH;

      function __construct(){
        include_once "connection.inc.php";
        $this->DBH = $DBH;
      }

      function getColor($id){
        $this->DBH // <---- use it like this instead of your $DBH old variable.
      }
  }
?>

This is wrong. This class cannot be unit tested because there is no way to mock $DBH. — Tomas Javaišis, Apr 27 '17 at 04:24

score 0 · Accepted Answer · answered Apr 24 '17 at 19:31

0

Let's say you have a class named House with a getColor() method, and in your index.php. You can use the keyword global inside your function/method, but I am strongly against this. Example:

public function getColor(int $id)
{
    global $dbh;
    //and use it as $dbh
    $dbh->prepare(....
 }

Or you can inject it in the constructor. Example of how your class will look like

class House
{

    private $dbh;
    function __construct($dbh)
    {
         $this->dbh = $dbh;
    }

    public function getColor($id)
    {
       //$this refers to current object context
        $this->dbh->prepare.....
    }
}

And when you instantiate the House object you will pass the $DBH into the constructor. Example for your index.php:

include_once "connection.inc.php";
$house = new House($DBH);
$house->getColor($id);

Although, I suggest that you checkout Domain Driven Design, Factory and Repository pattern, and ORM like Doctrine or Eloquent to get more understanding on how to separate your application/domain logic from the database.

answered Apr 24 '17 at 19:31

frz3993

1,595
11
13

Why include the global approach in your answer if you are strongly against it? – Don't Panic Apr 24 '17 at 19:36
Thank you! This is exactly what I was searching for!! – Tobi Apr 24 '17 at 19:41
OP might encounter something like that in the future, so to advise against it I should give an example of how it looks like. Don't you think @Don'tPanic? – frz3993 Apr 24 '17 at 19:49
Sure, that makes sense. – Don't Panic Apr 24 '17 at 19:53
I would use static property since it doesn't need to be replicated for every instance – Whip May 23 '22 at 03:13

score -2 · Answer 3 · edited Jul 08 '20 at 11:56

class Database
{
    private $host = "localhost";
    private $dbname = "codeignitor";
    private $username = "root";
    private $password = "";
    public $conn;

    public function getConnection()
    {
        $this->conn = null;
        try {
            $this->conn = new PDO ("mysql:host=" . $this->host . ";dbname=" . $this->dbname, $this->username, $this->password);
            $this->conn->exec("set names utf8"); 
            // echo "MySqlConnected";
        } catch(PDOException $exception){ 
            echo "Connection error: " . $exception->getMessage(); 
        } 
            return $this->conn; 
    } 
}

How to use database connection in other classes

3 Answers3