Why did replacing all my "mysql" with "mysqli" stop my project?

Question

What should I do? I must configure in the database?

Before everything worked normally, user registration, login...

<?php
   $host ="localhost";
   $user ="root";
   $pass ="senha"; 
   $banco="usuarios";

   $conexao = mysqli_connect($host, $user, $pass) or die (mysqli_error());
   mysqli_select_db($banco) or die (mysqli_error()); 
?>

Answer 1

Here I present according to the documentation one of the exact ways of working with mysqli_ which is quite different from the primary consultations of mysql. First, you can already write the variables directly within the instruction as follows and apply the demonstrated method: Make the connection and store it within a variable.

// Conexão com o banco de dados
$conecta = mysqli_connect("host", "usuario", "senha", "banco") or die("Error " . mysqli_error($conecta)); 

// Faça então qualquer operação do CRUD seguindo as diretivas abaixo: 
$consulta = "SELECT * FROM usuarios" or die("Error in the consult.." . mysqli_error($consulta)); 

// Execute a consulta 
$resultado = $conecta->query($consulta); 

This is just the basis for working with mysqli_ and you also have another option that is PDO. I’m also adding a while if you need to return data for comparison:

while($linha = $resultado -> fetch_assoc()){
    echo '<p>'.$linha["nome"].'</p>';
    echo '<p>'.$linha["cpf"].'</p>';
    // etc ...
}; 

Answer 2

You probably use native functions throughout the code: mysql_query, mysql_fetch_array, mysql_num_rows and etc...

So to change, for example, from: mysql_query for mysqli_query, you also need to change the arguments, passing the link in the first argument and the query string in the second argument, and not just the query string as it was before, and this makes you have to modify ALL the website querys.

So since you are obliged to modify almost everything, I suggest you already make the modifications according to the concept I explain below.

I usually create functions for all DB operations, so when some modification is needed, I only modify my functions and do not need to change anything in the rest of the code, this was very useful when I had to change mysql_ for mysqli_, below an example:

include('db_functions.php');

$host ="localhost";
$user ="root";
$pass ="senha"; 
$banco="usuarios";

jaw_db_connect($host, $user, $pass, $banco);

$cliente_query = jaw_db_query("select * from clientes where email = '" . jaw_db_input($email_address) . "'");

if (jaw_db_num_rows($cliente_query) > 0) {
    $cliente = tep_db_fetch_array($cliente_query);

} else {
    // nenhum cliente
}

db_functions.php

  function jaw_db_connect($server, $username, $password, $database, $link = 'db_link') {
    global $$link;

    $$link = mysqli_connect($server, $username, $password, $database);

    return $$link;
  }

  function jaw_db_error($query, $errno, $error) { 
    die('<div><b>' . $errno . ' - ' . $error . '</b></div><div>' . $query . '</div>');
  }

  function jaw_db_query($query, $link = 'db_link') {
    global $$link;

    $result = mysqli_query($$link, $query) or jaw_db_error($query, mysqli_errno($$link), mysqli_error($$link));

    return $result;
  }

  function jaw_db_fetch_array($db_query) {
    return mysqli_fetch_array($db_query, MYSQLI_ASSOC);
  }

  function jaw_db_num_rows($db_query) {
    return mysqli_num_rows($db_query);
  }

  function jaw_db_input($string, $link = 'db_link') {
    global $$link;
    return mysqli_real_escape_string($$link, $string);
  }

I put up only the main functions, but just include all the functions you will use on the site...

Using this system, you can easily modify the function jaw_db_query for it to record in a log file all the querys and their execution time, count how many querys were executed in the page, add the total time and record in a variable for you to display in the footer in development environment, and this helps a lot to identify low-performance querys, which can cause server overload...

Answer 3

It is necessary to pass two arguments to mysqli_select_db(), the first the connection and the second the name of the bank, as suggested in link passed by @marcosvinicius

mysqli_select_db($conexao, $banco);

Or make the connection by passing the bank name in this way:

$conexao = mysqli_connect($host, $user, $pass, $banco);