Generating valid Php Array for json conversion

Question

Explaining a bit of the purpose of the code: Through the sql query returns data, the only data needed is the 'id' and the name of the 'area', then two arrays are created, one to receive the 'id’s and the other to receive area’s, after that the two arrays will be placed in only one array, id becomes the key, and area becomes the value respectively in the same order. Convert the generated array to json.

This snippet is not converting the PHP array to json: "echo json_encode($c); "

Nothing appears on the screen. Apparently the array is not valid for converting. How to perform this conversion in a valid way?

            $id = 22;
            function listaAreas($conexao,$id)
            {
                $areasArray = array();
                $query = "SELECT * FROM ciencias JOIN areas on ciencias.id=areas.areaCiencia WHERE ciencias.id={$id}";
                $resultado = mysqli_query($conexao,$query);
                    while ($ciencia = mysqli_fetch_assoc($resultado))
                    {
                        array_push($areasArray, $ciencia);
                    };
                    return $areasArray;
            };


            $areasArray = listaAreas($conexao,$id);
            $arrayIds = array();
            $arrayAreas = array();
            foreach ($areasArray as $key => $value)
            {
                foreach ($value as $a => $b)
                {
                     if($a == "id")
                     {
                        array_push($arrayIds,"{$b}");
                     };

                     if($a == "area")
                     {
                        array_push($arrayAreas,"{$b}");
                     };
                };
            };

            $c = array_combine($arrayIds, $arrayAreas);
            echo json_encode($c);

If you give a:

            echo "<pre>";
            var_export($c);
            echo "</pre>";

Output:

            array (
              1 => 'Direito Administrativo',
              2 => 'Direito Ambiental',
              3 => 'Direito Civil',
              4 => 'Direito Constitucional',
              5 => 'Direito do Consumidor',
              6 => 'Direito do Trabalho',
              7 => 'Direito Empresarial',
              8 => 'Direito Internacional',
              9 => 'Direito Penal',
              10 => 'Direito Processual Civil',
              11 => 'Direito Processual do Trabalho',
              12 => 'Direito Processual Penal',
              13 => 'Direito Tributário',
              14 => 'Direitos Humanos',
              15 => 'Estatuto da Criança e do Adolescente',
              16 => 'Ética Profissional',
              17 => 'Filosofia do Direito',
            )

Answer 1

Follow its refactored code to simplify testing and eliminate possible points of failure. One of the possibilities for the json_encode fail is to receive data with non-ASCII characters that are not in UTF-8:

ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

$id = 22;
function listaAreas($conexao,$id)
{
    $areasArray = array();
    $query = "SELECT * FROM ciencias JOIN areas on ciencias.id=areas.areaCiencia WHERE ciencias.id=".$id;
    $resultado = mysqli_query($conexao,$query);
    if mysqli_errno($conexao)
    {
        die( mysqli_error($conexao) );
    }
    while ($ciencia = mysqli_fetch_assoc($resultado))
    {
        //$areasArray[$ciencia['id']] = utf8_encode( $ciencia['area'] );
        $areasArray[$ciencia['id']] = $ciencia['area'];
    };
    return $areasArray;
 };

$c = listaAreas($conexao,$id);

echo 'ARRAY<br>';
print_r( $c );
echo 'JSON<br>';
print_r( json_encode( $c ) );

If the data is not in UTF-8, adjust the line inside the while for that:

 $areasArray[$ciencia['id']] = utf8_encode( $ciencia['area'] );

Assuming DB has the fields id and area, this code should work with the same result as the previous one (including with the Ncode working), although much leaner.

Expected result:

{
 "1":"Direito Administrativo",
 ...
 "15":"Estatuto da Crian\u00e7a e do Adolescente",
 "16":"\u00c9tica Profissional","17":"Filosofia do Direito"
}