text status=:parsererror, error thrown:=SyntaxError: Unexpected token < in JSON at position 0

$.ajax({
        url: 'private/ajax/get_personas.php',
        type:'GET',
        contentType: 'application/json; charset=utf-8',
        dataType:'JSON',
        success: function(data, textStatus, jqXHR) {
            alert(data);
        },
        error: function(data, textStatus, errorThrown) {
            console.log('message=:' + data + ', text status=:' + textStatus + ', error thrown:=' +  errorThrown);
        }
    });

include('private/connection.php');
echo json_encode("hello");

$host = "localhost";
$user = "root";
$pass = "12345";
$db = "pruebas";
$port = 3306;

$connection = mysqli_connect($host, $user, $pass, $db, $port);

echo json_encode($texto);

$.ajax({
    url: 'private/ajax/get_personas.php',
    type: 'GET',
    success: function(data, textStatus, jqXHR) {
        console.log(textStatus, jqXHR, data);
    },
    error: function(data, textStatus, errorThrown) {
        console.log('message=:' + data + ', text status=:' + textStatus + ', error thrown:=' + errorThrown);
    }
});