Can't echo out rows from database Class using PDO, get 'ArgumentCountError'

Question

I'm trying to echo out data from my database through my Retrieve Class using PDO. I'm having trouble doing that. Can someone please help me?

This error shows:

Fatal error: Uncaught ArgumentCountError: Too few arguments to function Retrieve::__construct(), 0 passed in index.php on line 89 and exactly 1 expected in index.php:58 Stack trace: #0 index.php(89): Retrieve->__construct() #1 {main} thrown in index.php on line 58

This is my code:

<?php 
class Database {
 private $host = 'localhost';
 private $db_name = 'photos';
 private $username = 'root';
 private $password = '';
 private $conn;

 public function connect() { 

  try {
   $this->conn = new PDO('mysql:host=' . $this->host . ';dbname=' . $this->db_name, $this->username, $this->password);
   $this->conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
   echo "Connected successfully"; 
  } catch(PDOException $e) {
   echo 'Connection Error: ' . $e->getMessage();
  }

  $this->conn = null;
 }

}

class Retrieve extends Database {
 
 private $conn;
 private $table = 'indeximg';

 public $id;
 public $username;
 public $img;

 public function __construct($db) {
  $this->conn = $db;
 }

 public function read() {
  $query = 'SELECT id, username, img FROM' . $this->table;
  $stmt = $this->conn->prepare($query);
  $stmt->execute();
  return $stmt;
 }

}


$object = new Retrieve;
echo $object->read();
?>

score 1 · Answer 1 · answered Sep 25 '18 at 04:13

From your code, the constructor for Retrieve expects one argument: $db, and you didn't pass any when you created an instance here:

$object = new Retrieve; // <-- where is the argument?
echo $object->read();

Your code is confusing at this point. If the Retrieve class expects an instance of Database in the constructor, why does it extend the Database class?

Try this:

<?php 
class Database {
    private $host = 'localhost';
    private $db_name = 'photos';
    private $username = 'root';
    private $password = '';
    private $conn;

    public function connect() { 

        try {
            $this->conn = new PDO('mysql:host=' . $this->host . ';dbname=' . $this->db_name, $this->username, $this->password);
            $this->conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            echo "Connected successfully"; 
        } catch(PDOException $e) {
            echo 'Connection Error: ' . $e->getMessage();
        }

        $this->conn = null;
    }

}

class Retrieve {

    private $conn;
    private $table = 'indeximg';

    public $id;
    public $username;
    public $img;

    public function __construct($db) {
        $this->conn = $db;
    }

    public function read() {
        $query = 'SELECT id, username, img FROM' . $this->table;
        $stmt = $this->conn->prepare($query);
        $stmt->execute();
        return $stmt;
    }

}


$db = new Database();
$db->connect();
$object = new Retrieve($db);
echo $object->read();
?>

I removed the inheritance of Retrieve and passed the proper constructor argument to Retrieve.

I borrowed some of this code from a tutorial, I just added on my own code. You were able to fix the first error I got (thank you very much), but now I'm getting another error. — codo7081, Sep 25 '18 at 04:25
Connected successfully Fatal error: Uncaught Error: Call to undefined method Database::prepare() in index.php:39 Stack trace: #0 index2.php(50): Retrieve->read() #1 {main} thrown in index.php on line 39 I'm not sure how to fix this — codo7081, Sep 25 '18 at 04:27
If you look at the Database class, there is no "prepare" method defined there, only "connect". It looks like you didn't fully import the class from the tutorial. — Raisen, Sep 25 '18 at 04:34
This is still too confusing to me. I'll try to resolve this, thank you for your advice, is very helpful — codo7081, Sep 25 '18 at 04:48

Deno · Answer 2 · 2018-09-25T04:42:07.587

0

Argument missing on.

$object = new Retrieve;
//Should be $object = new Retrieve($your_db);

You have requested an argument on

public function __construct($db) {
        $this->conn = $db;
    }

And since you already inherited from parent

Why don't just add $this->connect() in your __construct instead of

$db = new Database();
$db->connect();
$object = new Retrieve($d);
echo $object->read();

edited Sep 25 '18 at 04:42

answered Sep 25 '18 at 04:06

Deno

434
4
16

Thanks for fixing the issue but now I'm getting another error. It is: Connected successfully Fatal error: Uncaught Error: Call to undefined method Database::prepare() in index.php:39 Stack trace: #0 index2.php(50): Retrieve->read() #1 {main} thrown in index.php on line 39 – codo7081 Sep 25 '18 at 04:28
@codo7081 I've updated my answer, – Deno Sep 25 '18 at 04:48
I've tried that too but I'm still getting errors. Thanks for your help I'll find out how to fix it. – codo7081 Sep 25 '18 at 05:13
@codo7081 can show me your class Retrieve ? – Deno Sep 25 '18 at 06:14

Can't echo out rows from database Class using PDO, get 'ArgumentCountError'

2 Answers2