"expects Parameter 2 to be Resource" error when connecting to the database

Question

I am trying to make a connection via php to a mysql server but always presents the following error:

Warning: mysql_select_db() expects Parameter 2 to be Resource, null Given in /home/u517649386/public_html/conecta.php on line 6

The code used is as follows::

<?php
$banco = new PDO('mysql:host=mysql.hostinger.com.br;u517649386_teste', 'u517649386_teste','senha')or die(mysql_error());
print "Conexão efetuada com sucesso!";


mysql_select_db('u517649386_teste', $con);
print "Conexão e Seleção OK!"; 


if($_GET['acao'] == 'listapizzas'){

     $sql = "SELECT * FROM `pizzas` LIMIT 0, 30 ";

     $re = mysql_query($SQL, $serve);

     $num = mysql_num_rows($re);

     if($num > 0){

           while($Linha = mysql_fetch_object($re)){
                  echo "{$Linha->Nome}<br />";
           }

      }
      else{
          echo 'nenhuma pizza cadastrada';
      }
}
?>  

The php version of the server is 5.5.35

Answer 1

There are three ways to make PHP connect with Mysql, the functions (removed from php7) mysql, the PDO and the Mysqli. Question code mixed PDO with removed functions.

The simplest solution would be to use Mysqli.

$banco = new mysqli_connect('localhost', 'usuario', 'senha', 'banco');

if($_GET['acao'] == 'listapizzas'){

     $sql = "SELECT * FROM `pizzas` LIMIT 0, 30 ";

     $re = mysqli_query($banco, $sql);

     $num = mysqli_num_row($re);

     if($num > 0){
        while($Linha = mysqli_fetch_object($re)){
           echo "{$Linha->Nome} <br />";
        }
      }else{
         echo 'nenhuma pizza cadastrada';
      }
}

Answer 2

The $con variable is null and the mysql native functions do not work with PDO. Try this way: `

   <?php

$serve = mysqli_connect('127.0.0.1', 'root', 'senha','banco'); // Se vc indica o banco aqui não precisa selecionar depois

if ($serve->connect_errno) {
    printf("Erro: %s\n", $serve->connect_error);
    exit();
}


if($_GET['acao'] == 'listapizzas'){

     $SQL = "SELECT * FROM tipos";

     $re = $serve->query($SQL, , MYSQLI_USE_RESULT);

    if(mysqli_num_rows($re)<1){
        printf("Sem registros!");
    } else {
        // Laço
         while ($obj=mysqli_fetch_object($re)){
             printf("%s (%s)\n",$obj->Nome);
         }

          mysqli_free_result($re);
    }

}
?>