Error in consultation

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What is wrong?

I did everything right, researched and resumed the mistake:

Notice: Trying to get property 'num_rows' of non-object in C:\xampp\htdocs\tipo\consulta-online.php on line 21

What can it be?

<?php

    $servidorBanco = "localhost";
    $usuarioBanco = "root";
    $senhaBanco = "12345";
    $dadosBanco = "bancodedados";

    $conexao = mysqli_connect($servidorBanco, $usuarioBanco, $senhaBanco, $dadosBanco);

    if(!$conexao){
        die("Falha na conexao: " . mysqli_connect_error());
    }else{
        //echo "Conexao realizada com sucesso";
    }   

    $sql = "SELECT * FROM sis_clientes";
    $result = $conexao->query($sql);

    if ($result->num_rows > 0) {

       while($row = $result->fetch_assoc()) {

           //É isso que eu quero que consulta, quero que consulte 
           //todos os dados refere a esse campo da tabela "login"
           echo $row["login"];

        }
    } else {
        echo "0 results";
    }
    $conexao->close();
?>
php mysql

  • Check if the table actually exists. If it exists, add a die($conexao->error); after $conexao->query.

  • Gave this error. Parse error: syntax error, Unexpected 'die' (T_EXIT) in C: xampp htdocs query-online.php on line 17

  • i did so. $result = $connected->query($sql) die($connected->error);

  • And tbm tried so. $result = $connected->query($sql); $result = $connected->error; Also no results.

  • Missed the or. The correct is $result = $conexao->query($sql) or die($conexao->error);

  • Show amigo, that was it. Problem was that in the database name was sis_clientes and was sis_cliente, thanks. My vote is yours. Put your answer I will add the vote as completed.

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1 answer

1


This error happens when there is an error in query.

The method query of extension MySQLi, can return 3 results:

  • false: In case of failure, for example, when the query is invalid;
  • MySQLi_Result: If successful for the darlings of the kind SELECT, SHOW, DESCRIBE or EXPLAIN;
  • true: If successful for the darlings other than those mentioned in the previous item, for example, insert and update.

When we use a query valid, however, with the table name or different fields, the method query returns us a false and so we can’t access the property as num_rows.

That is why it is important that we use verification with mysqli_error or $conn->error. It is obviously necessary to use this practice carefully. Ideally you store these values in a log and treat the message to the customer, for example:

<?php

$conexao = mysqli_connect("localhost:3307", "root", "123456", "teste");

$sql = "SHOW TABLE;"; /* Erro proposital */
$result = $conexao->query($sql);

if ($conexao->error) {
    Log::warning( $conexao->error );
    die("Não foi possível completar a operação. Entre em contato com um adminstrador do site.");
}

This will prevent malicious people from getting errors from their application. So only you, the developer, will know the errors and can fix them in your application.

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