Uncaught TypeError: PDO::__construct() expects parameter 1 to be string

Question

I have searched the forum, but I have not found anything directly related to my issue. I am fairly new to PDOs and class OOP creation. I am trying to create a database connection class where I can instantiate the connection as needed. I having issues instantiating my connection.

File Organization:

parent directory (folder)
      |     
      private (folder)
            |
            config.php
             classes (folder)
                     |
                     class1.class.php
                     DatabaseConnection.class.php
                     db_cred.inc.php
      public (folder)
           |
           search.php

Process:

• I have created a database credential php file "db_cred.inc.php"
• I have a database connection class called "DatabaseConnect" in "DatabaseConnect.class.php" file
• I load those files as follows
  • require_once 'db_cred.inc.php'; in the "DatabaseConnect.class.php" file
  • spl_autoload_register for all of my class files

Expected actions:

1. When my "search.php" page request data from mysql via a pdo, a new database connection will instantiate a new connection via the "openConnection()" method.
2. The class "DatabaseConnection" will load the credentials from "db_cred.inc.php" as a sting and connect to the database
3. The class will then use the credentials to connect to the mysql database, and execute the requested pdo query returning the results and storing them into a variable "$row".

Issue: When I execute the pdo, the following error is returned: Uncaught TypeError: PDO::__construct() expects parameter 1 to be string, array given in private/classes/DatabaseConnect.class.php:21 Stack trace: #0 private\classes\DatabaseConnect.class.php(21): PDO->__construct(Array) #1 \public\search.php(53): DatabaseConnect->openConnection() #2 {main} thrown in \private\classes\DatabaseConnect.class.php on line 21

spl_autoload_register() in the config.php file

  function my_autoload($class) {
    if(preg_match('/\A\w+\Z/', $class)) {
      require ('classes/' . $class . '.class.php');
    }
  }
  spl_autoload_register('my_autoload');

Credential setup in "db_cred.inc.php"

<?php

// define an array for db connection.
define("DB", [
  "DB_HOST" => "mysql:host=localhost",
  "DB_USER" => "user",
  "DB_PASS" => "pass",
  "DB_DATABASE" => "mytestdb",
  "DB_CHAR" => "utf8",
]);
?>

My class for database connection:

<?php
require_once 'db_cred.inc.php';

// creating db connection class

class DatabaseConnect {

private $server = 'DB_HOST';
private $database = 'DB_DATABASE';
private $pass = 'DB_PASS';
private $user = 'DB_USER';
private $opt = [
  PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
  PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
  PDO::ATTR_EMULATE_PREPARES   => false,
];

protected $con;

public function openConnection() {

**ERROR TAKES PLACE HERE**

  try {
    $this->con = new PDO([$this->server, $this->database, $this->user, $this->pass]);
      return $this->con;
  } catch(PDOExeption $e){
    echo "ERROR: " . $e->getMessage(), (int)$e->getCode();
  }
}
public function closeConnection() {
     $this->con = null;
  }
}

 ?>

PDO for search.php

<?php

$dbconn = new DatabaseConnect();
$pdo = $dbconn->openConnection();

$sql = "SELECT * FROM report";
foreach ($pdo->query($sql) as $row) {
  echo " PI: ".$row['pi'] . "<br>";

}
?>

I am not sure what is causing the error. I am sure it is due to my inexperience with classes and oop. It appears that the config.php file is working fine. The class is identified by the request because the error happens inside the PDO __construct method. Please help.

UPDATE - MY WORKING SOLUTION

I hope this might help someone moving forward with a similar question. I am not finished with the development of this process, but this kicked in a huge door.

My revised class

<?php
// Associating db_cred.inc.php with class
require_once('db_cred.inc.php');

// Creating db connection class
class DatabaseConnect {
/*
!! Assigning defined constants per define('DB_CONSTANT', 'value') loaded from "db_cred.inc.php" file to variables
!! "db_cred.inc.php" should not be loaded into the "config.php" file
!! BECAUSE THE VALUES OF THE VARIABLES ($variable) ARE CONSTANTS (DB_CONSTANT), DO NOT USE SINGLE OR DOUBLE QUOTES. THE PDO __CONSTRUCT FUNCTION WILL IGNORE  THE VALUE OF THE VARIABLE
*/
private $host =  DB_HOST;
private $database = DB_DATABASE;
private $pass = DB_PASS;
private $user = DB_USER;
private $char = DB_CHAR;
// Setting attributes and storing in variable $opt
private $opt = [
  PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
  PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
  PDO::ATTR_EMULATE_PREPARES   => false,
];
// $con variable will store PDO connection and is set to NULL
private $con;

// Create Connection to database
public function openConnection() {
  // Setting $con to null
$this->con = NULL;

// If $con is not NULL make it NULL
if ($this->con === NULL){
  try {
    // Establish DSN
    $dsn = "mysql:host={$this->host};dbname={$this->database};charset={$this->char}";
    // Complete the PDO connection
    $this->con = new PDO($dsn, $this->user, $this->pass,$this->opt);
    // Return the connection and store it in $con
      return $this->con;
      // Catch any exceptions and store in $e
  } catch(PDOExeption $e){
    // Echo error and Exception message
    echo "ERROR: " . $e->getMessage(), (int)$e->getCode();
  }
  // If the try/catch block fails, echo that no connection was established
} else {
  echo "ERROR: No connection can be established";
}
}
// Close connection and set it to NULL
public function closeConnection() {
     if($this->con !== NULL){
     $this->con = NULL;
   }
  }

// create CRUD subclass (Create, Read, Update, Delete)
}
 ?>

I changed "db_cred.inc.php" eliminating the array. I may revisit the idea.

<?php

// defining DB Credential CONSTANTS to be stored in variables and instantiated by connect class
define("DB_HOST", "localhost");
define("DB_USER", "user");
define("DB_PASS", "pass");
define("DB_DATABASE", "mytestdb");
define("DB_CHAR", "utf8");

// define an array for db connection.
/*define("DB", [
  "DB_HOST" => "localhost",
  "DB_USER" => "user",
  "DB_PASS" => "pass",
  "DB_DATABASE" => "mytestdb",
  "DB_CHAR" => "utf8",
]);*/

?>

Answer 1

The error explains itself: You're passing an array where you should be using a string instead.

You need to change this line:

$this->con = new PDO([$this->server, $this->database, $this->user, $this->pass]);

To this, (specifies the DSN first):

$dsn = "mysql:dbname={$this->database};host:{$this->host}";

$this->con = new PDO($dsn, $this->user, $this->password);