PHP和MYSQL：查询在具有值的列上返回null

Question

I have a problem with a simple SQL query:

SELECT a.idElemento, b.nombre, b.descripcion
FROM productos_elementos a
    INNER JOIN elementos_adicionales b
        ON a.idElementoAdicional=b.id_elemento_adicional
    INNER JOIN precio_elemento c
        ON a.idElemento=c.idElemento
WHERE a.idProducto = 1 AND c.idPolitica = 1

When I execute this query on my database, it returns:

IdElemento Nombre  Descripcion
    1        p1       p1_desc
    2        p2       p2_desc

However my PHP code returns me this values:

IdElemento Nombre  Descripcion
    1       null       null
    2       null       null

I don't know why that it's happening. Any ideas? This is the code:

//$query is a string with the querty: SELECT....
$result = $this->conn->query($query);
$aux = $result->fetchAll(PDO::FETCH_OBJ);
$results_to_send = json_encode($aux);

If I print the $variable $results_to_send at this moment, it is initialized to:

[{"idElemento":"1","nombre":null,"descripcion":null},{"idElemento":"2","nombre":null,"descripcion":null}]

I use the values in this piece of code:

foreach ($results_to_send as $key => $value){
...
echo $value->idElemento //It prints 1 or 2
...
echo $value->nombre //It is null
...}

UPDATE: Finally I have found the problem. I don't know how to resolve it yet, but it's a start.

The problem is the string stored in the database. Both columns have characters with accents. For example the first row is: (1,p1_náme, p1_désc). It returns (1, null, null)

If I change it for (1,p1_name, p1_desc), it returns (1,p1_name, p1_desc).

UDATE 2: Problem solved thanks to Andrew Mackrodt comment ^^

Answer 1

I had the same problem which was caused by non-matching charsets between PHP's MySQLI and MySQL Database. Not all charsets have the same characters which can cause PHP to return a null.

You can compare and set your charset by locating your database charset (in phpmyadmin or in a query like this ) and set in PHP using $mysqli::set_charset("short_name") ( http://php.net/manual/en/mysqli.set-charset.php )

If you'd like to see what charsets are available here's a list. http://dev.mysql.com/doc/refman/5.6/en/charset-charsets.html

Answer 2

For PDO just do:

$db = new PDO("mysql:host=host.address.com.br; dbname=yourdb; charset=utf8;", "username", "password");
$db->exec("set names utf8");

and don't forgot to define Collation as utf8 too.

See this answer