a "real" and useful example of FETCH_SERIALIZE

<?php

//table example: https://gist.github.com/celsowm/82cace3ae81fdaf653a3e944007892bc

include 'conexao.php';

class Log implements \Serializable {

    public $id;
    public $dados;

    public function serialize() {
        return serialize((array) $this);
    }

    public function unserialize($serialized): void {

        foreach (unserialize($serialized) as $p => $v) {
            $this->{$p} = $v;
        }
    }

}

/*$log = new Log();
$log->id = 1;
$log->dados = ['usuario'=>'maria', 'metodo'=> 'incluirLivro', 'parametros' => ['preco'=> 7.99, 'titulo'=> 'Livro de Teste']];

$log2 = new Log();
$log2->id = 2;
$log2->dados = ['ip'=> '10.120.100.210', 'origem' => 'CHINA'];

var_dump(serialize($log2));*/


$statement = $pdo->query('SELECT dados FROM log');
$statement->setFetchMode(PDO::FETCH_CLASS|PDO::FETCH_SERIALIZE, Log::class);
$logs = $statement->fetchAll();
foreach ($logs as $log) {
    echo "id: $log->id | ";
    echo "dados: " . var_export($log->dados, true);
    echo "<br/>";
}