select

<?php


    class Database{

    // specify your own database credentials
    private $host = "127.0.0.1";
    private $db_name = "sisim";
    private $username = "root";
    private $password = "";
    public $conn;
    private $table_name = "cadastro_emp";


    // get the database connection
    public function getConnection()
    {

        $this->conn = null;

        try {
            $this->conn = new PDO("mysql:host=" . $this->host . ";dbname=" . $this->db_name, $this->username, $this->password);
        } catch (PDOException $exception) {
            echo "Connection error: " . $exception->getMessage();
        }

        return $this->conn;
    }
}


    class Empresa{

    //base de dados e nome da tabela

    private $conn;
    private $table_name = "cadastro_emp";

    //propriendades da Classe

    public $razao_social;
    public $cnpj;
    public $inscricao_estadual;


    public function __construct($db){
        $this->conn = $db;
    }


/* tentei desta forma a função de Pesquisa

    public function pesquisarTudo(){
    $query =  $pdo->query("SELECT razao_social,cnpj,inscr_estadual from cadastro_emp;");
    echo ($query);

    while ($linha = $query->fetch(PDO::FETCH_ASSOC)) { echo "Nome: {$linha['razao_social']} - Cnpj: {$linha['cnpj']}  - inscr_estadual: {$linha[inscr_estadual]} <br />";


    }
*/

    /* e tentei desta forma a função Pesquisar

    function ler(){
        $query = "SELECT
                    razao_social,cnpj,iscr_estadual
                FROM
                    " . $this->table_name . "
                ORDER BY
                    name";
        echo $query;

        $stmt = $this->conn->prepare( $query );
        $stmt->execute();

        return $stmt;
    }


}
?>