How to write prepare and execute statements in OOP

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I have a little problem here.I am new to OOP, so the question might sound stupid, but I couldn't find any helpful information.

I am trying to login to the database and put the user's entered values inside of it and I want to ask you, in which place should I write PDO prepare and execute statements? I know they're needed, but I have no idea how to write it corretly...Besides that, I also got an error "Object of class PDO could not be converted to string on line 24". Thank you for any help, here's my code:

<?php
class Connection {
public $connection;
public $dbHost = 'localhost';
public $dbName = 'employees';
public $charset = 'charset=utf8';
public $dbUser = 'root';
public $dbPassword = '';

public function __construct() {
    try {
        $this->connection = new PDO ("mysql:host=$this->dbHost;$this->dbName;$this->dbUser;
        $this->dbPassword");
        $this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    }
    catch (PDOException $e) {
        echo "There is something wrong with the database".$e->getMessage();
    }
}
function insertUserValues($tableName, $data) {
    $query = "INSERT INTO ".$tableName."(";
    $query .= implode (",",array_keys($data)).') VALUES (';
    $query .= "'" . implode ("','",array_values($data))."')";
}
}
$users = new Connection();
?>

Answer 1

I'm not really good with explanations bru, but I just see that there's no answer after a long time. I have created a basic class for you to insert values using PDO, I hope it will point you to the correct direction, I will also share some useful links for you.

First the connect.

I can see you have done the connection already in your class, but below is the proper best pdo connection.

    $host = '127.0.0.1';
    $db   = 'YourDatabase';
    $user = 'YourDBUser';
    $pass = 'YourDBPass';
    $charset = 'utf8';

    $dsn = "mysql:host=$host;dbname=$db;charset=$charset";
    $opt = [
            PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_EMULATE_PREPARES   => false,
            ];

$dbh = new PDO($dsn, $user, $pass, $opt);

that is how you set up proper PDO connection. dns stands for data source name Reference of the above https://phpdelusions.net/pdo#dsn this guy explains it better. everything you need to know.

Now how do you put that connection all together with your class?

well I will create a file collect pdoClass.php and work from that class.

<?php
class Connection
{
    private $host = "127.0.0.1";
    private $dbName = "YourDB";
    private $user = "YourUser";
    private $pass = "YourPass";
    private $charset = 'utf8';

    private $dbh;
    private $error;
    private $stmt;

    //connection
    public function __construct()
    {
        $dsn     = "mysql:host=" . $this->host . ";dbname=" . $this->dbName . ";charset=" . $this->charset;
        $options = array(
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_EMULATE_PREPARES => false
        );

        try {
            // setup connection
            $this->dbh = new PDO($dsn, $this->user, $this->pass, $options);
        }
        //catch any errors
        catch (PDOException $e) {
            $this->error = $e->getMessage();
        }

    }

    //prepare statement
    public function insertUserValues($query)
    {
        $this->stmt = $this->dbh->prepare($query);
    }

    //bind values
    public function bind($param, $value, $type = null)
    {
        if (is_null($type)) {
            switch (true) {
                case is_int($value):
                    $type = PDO::PARAM_INT;
                    break;
                case is_bool($value):
                    $type = PDO::PARAM_BOOL;
                    break;
                case is_null($value):
                    $type = PDO::PARAM_NULL;
                    break;
                default:
                    $type = PDO::PARAM_STR;
            }
        }
        //actual value binding
        $this->stmt->bindValue($param, $value, $type);
    }
    //execute statement
    public function run()
    {
        return $this->stmt->execute();
    }
}

?>

basically that's all you need to setup the database and the function to insert in your db, I have tried to comment some sections.

Now to use this class create index.php or what ever you like. then include the class

<?php
    include'pdoClass.php';


    $users = new Connection();

    $users->insertUserValues('INSERT INTO test (name, age, description) VALUES(?,?,?)');
    $users->bind(1, 'User'); //bind each value
    $users->bind(2, 391); // bind
    $users->bind(3, 'This is a value');
    if($database->run()){

        echo "record inserted";
    }

?>

Done, if you have any question or like me to explain anything, feel free to comment below I will try my best to assist u.

Edit : if you need to fetch the results, you can also make a new function in the class,

Single row :

public function SingleRow(){
      $this->run();
      return $this->stmt->fetch();
  }

see we use fetch(); to only fetch one row. most people when they fetch results will fetch them like this fetch(PDO::FETCH_ASSOC) but because we did a proper connection and defined our default fetch mode in the connection we don't need all that we can just use fetch();

to display those results on your index.php file this is how you will do :

$users->insertUserValues("SELECT name, age, description FROM test WHERE name = :name");
$users->bind(':name','joe');
$row = $users->SingleRow();

echo '<pre>';
print_r($row);
echo '</pre>';

this will display joe's result as an array.

to get all the results from our db

we do another function to display all results.

 public function All(){
          $this->run();
          return $this->stmt->fetchall();
      }

You see the difference now we use fetchall() because we want all the results.

 $users->insertUserValues("SELECT *  FROM test");
    $row = $users->All();

    echo '<pre>';
    print_r($row);
    echo '</pre>';