PHP and JSON

$product = ['name' => 'Desk lamp', 'price' => 24.5, 'in_stock' => true];
echo json_encode($product);
// {"name":"Desk lamp","price":24.5,"in_stock":true}

• Associative arrays become JSON objects { }; indexed arrays (0, 1, 2...) become JSON arrays [ ].
• true, false and null become their JSON equivalents.
• Add flags for nicer output: JSON_PRETTY_PRINT adds line breaks and indentation, and JSON_UNESCAPED_UNICODE and JSON_UNESCAPED_SLASHES keep characters like é and / readable.

Combine flags with |: json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES).

$json = '{"name":"Ana","scores":[82,91]}';
$data = json_decode($json, true);
echo $data['name'];        // Ana
echo $data['scores'][1];   // 91

The second argument, true, gives you associative arrays, which most PHP code finds easiest. Without it, objects become stdClass objects and you read them with arrows: $data->name. Pick one style and use it consistently.

json_encode turns an object into a JSON object using only its public properties; private and protected ones are left out. To control exactly what an object looks like as JSON, implement the JsonSerializable interface:

class Product implements JsonSerializable {
    public function __construct(private string $name, private float $price) {}

    public function jsonSerialize(): array {
        return ['name' => $this->name, 'price' => round($this->price, 2)];
    }
}

echo json_encode(new Product('Pen', 1.2));   // {"name":"Pen","price":1.2}

Empty arrays need a little care. PHP can't tell whether an empty array is meant as a list or an object, so json_encode([]) gives []. If the receiving program expects an object, use (object) [] or the JSON_FORCE_OBJECT flag, both of which give {}. Clients written in strongly typed languages often break when the same field is sometimes [] and sometimes {}.

JSON from outside your program might be broken or incomplete. By default json_decode simply returns null, which is easy to miss. The modern, safer way is to ask PHP to throw an exception:

try {
    $data = json_decode($json, true, 512, JSON_THROW_ON_ERROR);
} catch (JsonException $e) {
    echo "Invalid JSON: " . $e->getMessage();
}

The 512 is the maximum nesting depth, which you'll rarely need to change. Exceptions are covered fully in the exceptions lesson.

Reading JSON from another service can be as simple as file_get_contents($url), although real projects usually use the cURL extension or a library such as Guzzle for timeouts and headers.

To build your own small API endpoint, set the right header and echo JSON:

header('Content-Type: application/json');
echo json_encode(['status' => 'ok', 'items' => $items]);

JavaScript on your page can then load it with fetch('/api/products.php'), exactly as in the JavaScript fetch lesson. Use http_response_code(404) or similar to signal errors properly.