public function prepareExecFetch() { ... }

public function prepareExec() { ... }

public function fetch() { ... }

$stmt1 = $pdo->prepare('...');
$stmt1->execute(array('...' => '...'));
$r1 = $stmt1->fetch(PDO::FETCH_ASSOC);

<?php
class DB {
    private $host;
    private $name;
    private $charset;
    private $user;
    private $password;

    // I wonder how could I store all the statements here, using the
    // $stmt1 = ...; $stmt2 = ...; wouldn't work cause it has to be
    // dymanic and I can't create new properties inside any method
    private $stmts = [];

    // Not using static modifier because if there was another instance of this
    // class, then $stmtCounter variable should be resetted again to 0
    private $stmtCounter = 0;

    public function __construct(string $host, string $name, string $charset,
                                string $user, string $password) {
        $this->host = $host;
        $this->name = $name;
        $this->charset = $charset;
        $this->user = $user;
        $this->password = $password;

        $pdo = new PDO('mysql:host=' . $this->host . '; dbname=' . $this->name . ';
                        charset=' . $this->charset, $this->user, $this->password);

        // While false, PDO will take advantage of the native prepared statement
        // functionality
        $pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);

        // In exception mode, if there is an error in SQL, PDO will throw
        // exceptions and the script will stop running
        $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    }

    public function execPrepareFetch(string $stmt, array $execParams) {
        $this->stmtCounter++;
        array_push($this->stmts, $stmt . $this->stmtCounter);
    }
}

// This way by instantiating multiple instances we can easily work with multiple
//databases
$db = new DB(DB_HOST, DB_NAME, DB_CHARSET, DB_USER, DB_PASSWORD);
$db->execPrepareFetch('$stmt', [':user' => 'some value']);