<?php
    require_once 'config.php';

    abstract class connect {
        protected $link;
        public function __construct($dbhost,$dbuser,$dbpass,$dbname2) {

            $host = $dbhost;
            $user = $dbuser;
            $password = $dbpass;
            $database = $dbname2;
            // $host = 'localhost';
            // $user = 'student';
            // $password = 'c@18504';
            // $database = 'practice';
            $this->link = @mysqli_connect($host, $user, $password, $database);
            if(!mysqli_connect_errno()) {

            } else {
                die("connection error: ".  mysqli_connect_error());

            }
        }
    }
?>

class connect {}

class connect {
    public function sumOrConcate($a, $b){
        return $a + $b;
    }
}

$conn = new connect();
$a = 15;
$b = 2;
echo $conn->sumOrConcate($a, $b); //17

//The variable names do not matter and in fact are not needed.
//$a and $b are for the scope of the function
echo $conn->sumOrConcate(8, 5); //13

class connect {
    public $a, $b;
    public function __construct($a, $b) {
        $this->a = $a;
        $this->b = $b;
    }
    public function sumOrConcate(){
        return $this->a + $this->b;
    }
}

$conn = new connect(12, 15);
echo $conn->sumOrConcate(); //27
// Since $a and $b are public you can set them
$conn->a = 2;
echo $conn->sumOrConcate(); //17
//If these were private you would need to create getter/setters.

abstract class connect {
  public function __construc($a, $b) {
    // use $a, $b
  }
}

// name of values can be different
$a = "value1";
$b = "value2";

$conn = new connect($a, $b);