Mysql select into PHP associative array not working

Question

I was trying to get the response from an SQL select statement but when I try to echo the array encoded to JSON I don't have anything written except the "-" I echo to ensure myself that is entering into the loop.

$sql = "SELECT * FROM PREGUNTA WHERE PREGUNTA.pregunta LIKE '%$palabra_clave%' OR PREGUNTA.respuesta_correcta LIKE '%$palabra_clave%' OR PREGUNTA.respuesta_falsa_1 LIKE '%$palabra_clave%' OR PREGUNTA.respuesta_falsa_2 LIKE '%$palabra_clave%' OR PREGUNTA.retroalimentacion LIKE '%$palabra_clave%'";
$query = mysqli_query($con, $sql);

$json = array();

while($data = $query->fetch_assoc()){
  $json[] = array(
      'pregunta' => $data['pregunta'],
      'respuesta_correcta' => $data['respuesta_correcta'],
      'respuesta_falsa_1' => $data['respuesta_falsa_1'],
      'respuesta_falsa_2' => $data['respuesta_falsa_2'],
      'retroalimentacion' => $data['retroalimentacion']
  );

    echo $data['pregunta'];
    echo '<br>';
}

echo json_encode($json);

And I this is my output:

¿Cuál no es un lenguaje de programación web?
¿Cuál es el lenguaje web más importante?

Have you checked your error logs? You're making an assumption the query is working. — Jay Blanchard
– Jay Blanchard, Commented Mar 15, 2016 at 12:16
@Jay Blanchard 5 I have cheked the error logs and I don't have any error about the query. Also if the query wouldn't be well written it wouldn't enter in the loop I think. — Juan Manuel Amoros
– Juan Manuel Amoros, Commented Mar 15, 2016 at 12:27
The query is the only explanation. How many times is the - echoed? Once? Definitely the query. — Jay Blanchard
– Jay Blanchard, Commented Mar 15, 2016 at 12:28
Add some error checking in your script - there are lots of scenarios where nothing will be written to mysql's error log, and nothing here which writes to the webserver error log. — symcbean
– symcbean, Commented Mar 15, 2016 at 12:37
Add as last line echo json_last_error_msg(); and tell us what you get. — trincot
– trincot, Commented Mar 15, 2016 at 13:37

Matt Raines · Accepted Answer · 2016-03-15 13:33:50Z

3

Most likely your input does not use the UTF-8 character encoding. According to the documentation for json_encode "All string data must be UTF-8 encoded".

When I pass an array containing "¿Cuál no es un lenguaje de programación web?" to json_encode, it works fine. But if I first convert the text to ISO-8859-1, json_encode returns boolean false and therefore outputs nothing.

Assign your variables to the array with (eg):

$json[] = array('pregunta' =>
    mb_convert_encoding($data['respuesta_correcta'], 'UTF-8', 'ISO-8859-1'),
    // ...
);

or convert your database and application to use UTF-8 to start with.

answered Mar 15, 2016 at 13:33

Matt Raines

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2 Comments

Juan Manuel Amoros Over a year ago

That was the problem. Now it works really good converting the encoding, but the server conection is in UTF8_general_ci, the database is in UTF8-spanish_ci and the tables are in UTF8-spanish_ci. Do you have any idea why I am having this problem?

Matt Raines Over a year ago

Have a browse through UTF-8 all the way through. Chances are something in your stack isn't configured to use UTF-8 correctly.

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