Setting up a database connection class in PHP

Question

I was recently introduced to the idea of classes in PHP, and after some research I've come to the conclusion that I need to store database related functions in a class to access later. It has worked for the most part, but some use cases I am still confused with. For example,

Below is an example of how I would normally connect to my database and display information from user id's in a table

dbcon.php:

<?php
$con = mysqli_connect("host","username","password","database") or die("Couldn't connect");

require_once("functions.php");
?>

functions.php

function getUserInfo($id) {
    $query = mysqli_query($con, "SELECT * FROM users WHERE id = '$id'");
    return mysqli_fetch_array($query);
}

Some random file:

require_once("dbcon.php");

$result = mysqli_query($con, "SELECT * FROM tablename");
while ($row = mysqli_fetch_assoc($result)) {
    $userinfo = getUserInfo($row['userid']);
    echo $userinfo['name'];
}

?>

I don't feel like this method of querying the database and displaying information is the neatest or most efficient way possible. I read this article about using classes to tamper with a database and call functions that I created in the class.

My first question is this: When I try to access $con in functions.php, it is undefined. How can I pass the variable from dbcon.php to functions.php over the require_once function?

I also would like to know what the best way to store my connection to the database is, and if there are any tutorials on how to set that up.

I hope you understood that lol.

Answer 1

You can do it like this way:-

Dbconnection.php:-

<?php
Class DbConnection{
    function getdbconnect(){
        $conn = mysqli_connect("host","username","password","database") or die("Couldn't connect");
        return $conn;
    }
}
?>

Function.php:-

<?php
require_once('Dbconnection.php');
Class WorkingExamples{
    function getUserInfo($id) {
        $Dbobj = new DbConnection(); 
        $query = mysqli_query($Dbobj->getdbconnect(), "SELECT * FROM users WHERE id = '$id'");
        return mysqli_fetch_array($query);
    }
}
$data = new WorkingExamples();
echo "<pre/>";print_r($data->getUserInfo(3));
?>

Note:- this is an example, try it by changing values according to your requirement and get the result.

Answer 2

 <?php
class Database{
   const DB_HOSTNAME = 'localhost';
   const DB_USERNAME = 'root';
   const DB_PASSWORD = 'root';
   const DB_NAME = 'stockganesha';
   public $_db_connect;
   protected $_sql;
   protected $_result;
   protected $_row;

   function db_connect(){
     $this->_db_connect = mysqli_connect(self::DB_HOSTNAME,self::DB_USERNAME,self::DB_PASSWORD,self::DB_NAME) or die(mysql_error());
     return $this->_db_connect;
   }

   function sql(){
       $this->_sql = 'SELECT * FROM customers';
   }

   function query(){
       $this->_result = mysqli_query($this->_db_connect,$this->_sql);
   }

   function fetch_array(){
       while($this->_row = mysqli_fetch_array($this->_result)){
           $username = $this->_row['first_name'];

           echo "<ul>";
               echo "<li>".$username."</li>";
           echo "</ul>";
       }
   }

   function db_close(){
       mysqli_close($this->_db_connect);
   }
}

and Import this in another class

<?php

require_once('../Config/Dbconnection.php');
include './model.php';

class CustomerDTO{

    private $mysql;
    function __construct() {
        $database = new Database();
        $this->mysql  = $database->db_connect(); 
    }
    function create($customer){
        $firstName = $customer->getFirstName();
        $lastName = $customer->getLastName();
        $emailId = $customer->getEmailId();
        $mobileNumber = $customer->getMobileNumber();
        $dateOfBirth = $customer->getDateOfBirth();
        $phoneNumber = $customer->getPhoneNumber();
        $termAndCondtion = $customer->getTermAndCondition(); 

       $result =  mysqli_query($this->mysql, "Insert into customers (first_name,last_name,email_id,mobile_number,date_of_birth,phone_number,term_and_condition)
       values('$firstName','$lastName','$emailId','$mobileNumber','$dateOfBirth','$phoneNumber','$termAndCondtion')");
        
       return $result;
    }

    function read(){
        $result = mysqli_query( $this->mysql, "Select * from customers");
        return $result;
    }

    function update($id, $customer){
        $result = mysqli_query($this->mysql, "update customers set 
            first_name = ".$customer->getFirstName()."
            last_name = ".$customer->getLastName()."
            email_id = ".$customer->getEmailId()."
            mobile_number = ".$customer->getMobileNumber()."
            date_of_birth = ".$customer->getDateOfBirth()."
            phone_number = ".$customer->getPhoneNumber()."
            term_and_condition = ".$customer->getTermAndCondition()."
            where id = ".$customer->getId());
        
        return $result;
    }

    public function delete($id){
      $result = mysqli_query($this->mysql, "delete from customers where id =".$id);
      return $result;
    }
}

Answer 3

<?php

class DatabaseConnection
{
    private $host       = "127.0.0.1";
    private $dbname     = "online_english";
    private $dbUsername = "root";
    private $dbPass     = "";
    private $charset    = 'utf8mb4';
    private $dsn;

    public function tryConnect(){
        try{
            $this->dsn = "mysql:host=$this->host;dbname=$this->dbname;charset=$this->charset";
            $DBH = new PDO($this->dsn,$this->dbUsername,$this->dbPass);
            $DBH->exec("set names utf8");
            $DBH->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            return $DBH;
        }
        catch (PDOException $e){
            $e->getMessage();
        }
    }
}
?>