Data type not defined in PHP

Question

Thinking of a banking system.

If I have a $balance variable; I can play a string within that variable in PHP.

I wonder how to solve this problem in php.

and what is the advantage of php having dynamic variable type.

Answer 1

PHP is dynamic, but even if it wasn’t, it doesn’t really define what will enter the database.

In PHP it is possible to control the input data, outside that the data coming from the database has the type of the value "approximated" to the same of the database (except some that turn string, for example BIGINT and DECIMAL), or when PHP is 32bit and mysql 64bit (which affects some "limits"), this may depend on the API you use (mysqli or Pdo), I’m not sure.

For example if you do this by reading data:

<?php
//Conecta
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

//Verifica se houve erros
if ($mysqli->connect_errno) {
    printf("Connect failed: %s\n", $mysqli->connect_error);
    exit;
}

//Query
$query = "SELECT id, nome, preco FROM Tabela LIMIT 1";

//Executa query
if ($result = $mysqli->query($query)) {

    /* Pega os dados */
    while ($row = $result->fetch_assoc())
    {
        //Exibe na tela, semelhante ao Symtem.out.println
        var_dump($row);
    }

    /* limpa resultados */
    $result->free();
}

/* fecha conexão */
$mysqli->close();

It returns something like this:

array(3) {
  ["id"]=> int(1)
  ["nome"]=> string(8) "carrinho"
  ["preco"]=> string(6) "100.02"
}

• id is INT and returned a type int
• nome is VARCHAR and returned string
• preco is DECIMAL and returned string

In the case probably DECIMAL turns into string because it turned float could lose the accuracy of the data, which would be a big headache

Note that even without typing the value is of a specific type in case the ID is still INT (as said I’m not sure of the situation for different processors and Apis)

However it is possible to pass data to query in a way that checks the input data:

<?php
$stmt = $mysqli->prepare("INSERT INTO Tabela VALUES (?, ?, ?, ?)");
$stmt->bind_param('isd', $id, $nome, $valor);

$id    = 2;
$nome  = 'Boneca';
$valor = 11.2;

/* execute prepared statement */
$stmt->execute();

printf("%d linhas inseridas\n", $stmt->affected_rows);

/* close statement and connection */
$stmt->close();

/* close connection */
$mysqli->close();

Behold:

• i corresponds to a type variable int
• d corresponds to a type variable double
• s corresponds to a type variable string
• b corresponds to a variable that contains data for a blob and sends in packets

Although when it comes to DECIMAL, it would be better to pass string even.

!!! I recommend you read this: Best kind of data to work with money? !!!

Concluding

mysql itself in a way makes the "CAST" when working a column of a specific type, this is independent of any language, so whether the language is dynamic or not is irrelevant in some way at the end.

Popular orms and the like

This is just an addendum, there are several Orms in PHP, like Propel, Doctrine and frameworks that have their own ORM systems, for example the Laravel, him through the Migrations can control the types of column values