Something

<?php 
require("json.php");
function response($array) {
    header('content-type: text/plain; charset=utf8');
    echo json::encode($array);
    exit(0);
}

    if (isset($_POST["nombre"])) {
        $response = array(
            'successMessage'    => 'That\'s correct!'
            
        );
    } else {
        $response = array(
            'errorMessage'        => 'Wrong answer!'
            
        );
    }
    response($response);

?>