Array in JSON are indexed array only, so the structure you're trying to get is not valid Json/Javascript.

PHP Associatives array are objects in JSON, so unless you don't need the index, you can't do such conversions.

If you want to get such structure you can do:

$indexedOnly = array();

foreach ($associative as $row) {
    $indexedOnly[] = array_values($row);
}

json_encode($indexedOnly);

Will returns something like:

[
     [0, "name1", "n1"],
     [1, "name2", "n2"],
]

json_encode() function will help you to encode array to JSON in php.

if you will use just json_encode function directly without any specific option, it will return an array. Like mention above question

$array = array(
  2 => array("Afghanistan",32,13),
  4 => array("Albania",32,12)
);
$out = array_values($array);
json_encode($out);
// [["Afghanistan",32,13],["Albania",32,12]]

Since you are trying to convert Array to JSON, Then I would suggest to use JSON_FORCE_OBJECT as additional option(parameters) in json_encode, Like below

<?php
$array=['apple','orange','banana','strawberry'];
echo json_encode($array, JSON_FORCE_OBJECT);
// {"0":"apple","1":"orange","2":"banana","3":"strawberry"} 
?>

To answer the actual question:

Why does PHP turn the JSON Object into a class?

Take a closer look at the output of the encoded JSON, I've extended the example the OP is giving a little bit:

$array = array(
    'stuff' => 'things',
    'things' => array(
        'controller', 'playing card', 'newspaper', 'sand paper', 'monitor', 'tree'
    )
);
$arrayEncoded = json_encode($array);
echo $arrayEncoded;
//prints - {"stuff":"things","things":["controller","playing card","newspaper","sand paper","monitor","tree"]}

The JSON format was derived from the same standard as JavaScript (ECMAScript Programming Language Standard) and if you would look at the format it looks like JavaScript. It is a JSON object ({} = object) having a property "stuff" with value "things" and has a property "things" with it's value being an array of strings ([] = array).

JSON (as JavaScript) doesn't know associative arrays only indexed arrays. So when JSON encoding a PHP associative array, this will result in a JSON string containing this array as an "object".

Now we're decoding the JSON again using json_decode($arrayEncoded). The decode function doesn't know where this JSON string originated from (a PHP array) so it is decoding into an unknown object, which is stdClass in PHP. As you will see, the "things" array of strings WILL decode into an indexed PHP array.

Also see:

• RFC 4627 - The application/json Media Type for JavaScript Object
• RFC 7159 - The JavaScript Object Notation (JSON) Data Interchang
• PHP Manual - Arrays

^{Thanks to https://www.randomlists.com/things for the 'things'}

Same answer, for PHP5.4+.

$foo = [
  "bar1" => (object)["",""],
  "bar2" => ["",""]
];

echo json_encode($foo);
// {"bar1":{}, "bar2":[]}

Another simple examples, with something important to notice:

$icons = (object)["rain"=>["💧"], "sun"=>["🌞"], "lightrain"=>["🌦"]];
echo $icons->sun;
// 🌞

$icons = (object)["rain"=>"💧", "sun"=>"🌞", "lightrain"=>"🌦"];
echo $icons->sun;
// 🌞

As Ray says if your class properties are protected or private, these will not be jsoned.

Since PHP 5.4 instead of using the commented toJson method, you have the ability to specify which data will be serialized implementing the JsonSerializable interface, so json_encode knows how to work on this.

/* PHP >= 5.4 only */
class Visits_Model_Visit implements JsonSerializable {
    public function jsonSerialize()
    {
        return array(
             'day' => $this->day,
             'date' => $this->date,
             'target' => $this->target,
             'id' => $this->id,
             'status' => $this->status,
        );
    }
}

just use only

$response=array();
$response["0"]=array("ip"     => "192.168.0.1",
                     "port"   => "2016");
$json=json_encode($response,JSON_FORCE_OBJECT);