I don't know why PDOStatement don't return "execution time" and "found rows" so here I created an extended class of PDOStatement with these attributes.

Just have to "setAttribute" of PDO's object to $PDO->setAttribute(\PDO::ATTR_STATEMENT_CLASS , ['\customs\PDOStatement', [&$this]]);

<?php

/**
*
*
*
*/

namespace customs;

/**
*
*
*
*/

final class PDOStatement extends \PDOStatement {

    /**
    *
    *
    *
    */

    protected $PDO = null;
    protected $inputParams = [];
    protected $executionTime = 0;
    protected $resultCount = 0;

    /**
    *
    *
    *
    */

    protected function __construct(PDO &$PDO) {
        $this->PDO = $PDO;
        $this->executionTime = microtime(true);
    }

    /**
    *
    *
    *
    */

    final public function getExecutionError(int $i = 2) {
        $executionError = $this->errorInfo();

        if (isset($executionError[$i]))
            return $executionError[$i];

        return $executionError;
    }

    /**
    *
    *
    *
    */

    final public function getExecutionTime($numberFormat = false, $decPoint = '.', $thousandsSep = ',') {
        if (is_numeric($numberFormat))
            return number_format($this->executionTime, $numberFormat, $decPoint, $thousandsSep);
        
        return $this->executionTime;
    }

    /**
    *
    *
    *
    */

    final public function getResultCount($numberFormat = false, $decPoint = '.', $thousandsSep = ',') {
        if (is_numeric($numberFormat))
            return number_format($this->resultCount, $numberFormat, $decPoint, $thousandsSep);
        
        return $this->resultCount;
    }

    /**
    *
    *
    *
    */

    final public function getLastInsertId() {
        return $this->PDO->lastInsertId();
    }

    /**
    *
    *
    *
    */

    final public function bindValues(array $inputParams) {
        foreach ($this->inputParams = array_values($inputParams) as $i => $value) {
            $varType = is_null($value) ? \PDO::PARAM_NULL : is_bool($value) ? \PDO::PARAM_BOOL : is_int($value) ? \PDO::PARAM_INT : \PDO::PARAM_STR;

            if (!$this->bindValue(++ $i, $value, $varType))
                return false;
        }

        return true;
    }

    /**
    *
    *
    *
    */

    final public function execute($inputParams = null) {
        if ($inputParams)
            $this->inputParams = $inputParams;

        if ($executed = parent::execute($inputParams))
            $this->executionTime = microtime(true) - $this->executionTime;

        return $executed;
    }

    /**
    *
    *
    *
    */

    final public function fetchAll($how = null, $className = null, $ctorArgs = null) {
        $resultSet = parent::fetchAll(... func_get_args());

        if (!empty($resultSet)) {
            $queryString = $this->queryString;
            $inputParams = $this->inputParams;

            if (preg_match('/(.*)?LIMIT/is', $queryString, $match))
                $queryString = $match[1];

            $queryString = sprintf('SELECT COUNT(*) AS T FROM (%s) DT', $queryString);

            if (($placeholders = substr_count($queryString, '?')) < count($inputParams))
                $inputParams = array_slice($inputParams, 0, $placeholders);

            if (($sth = $this->PDO->prepare($queryString)) && $sth->bindValues($inputParams) && $sth->execute())
                $this->resultCount = $sth->fetchColumn();
                
            $sth = null;
        }

        return $resultSet;
    }
}
?>

I think I found a way to execute a protected SQL query and at the same time find out the number of affected records.
I have the table 'tbl_users' with the following fields: id, login, password, age

<?
const DB_DRIVER = "mysql";
const DB_HOST = "localhost";
const DB_NAME = "my_db_name";
const DB_LOGIN = "root";
const DB_PASS = "root"; //OpenServer.

$connectionString = DB_DRIVER.':host='.DB_HOST.';dbname='.DB_NAME;
try
{
    //Connect to database.
    $db = new PDO($connectionString, DB_LOGIN, DB_PASS);
}
catch(PDOException $e)
{
    die("Error: ".$e->getMessage());
}
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

try
{
    
    //Decreasing age for user 'nick1'.
    $prep1 = $db->prepare("UPDATE tbl_users SET age=age-1 WHERE login='nick1'");

    //Increasing age for user 'nick2'.
    $prep2 = $db->prepare("UPDATE tbl_users SET \r\n age=age+1 WHERE login='nick2'");

    //Start transaction.
    $db->beginTransaction(); //Table type must be InnerDB!

    //We assume that everything will be fine.
    $flagDone = true; 

    //The exec() method returns the number of rows affected by the query.
    //$prep1->queryString is already an escaped SQL string.
    $result = $db->exec($prep1->queryString);
    if($result==false || $result!=1) //var_dump($result) - int(1) or bool(false).
        $flagDone = false;

    $result = $db->exec($prep2->queryString);
    if($result==false || $result!=1)
        $flagDone = false;

    if($flagDone)
    {
        if($db->commit())
            echo "Transaction was successful";
    }        
    else{
            echo "Transaction fail";
            $db->rollback();
    }
    echo "<br>";

}
catch(PDOException $e)
{
    die("Error: ".$e->getMessage());
}