public function __construct($config = [])
 {
     $this->sandBox = true;
     parent::__construct($config);
 }
<?php

require_once '../bootstrap.php';
use Dnetix\MercadoPago\MercadoPago;
/**
 * Searching payments for external reference.
 */
// Instanciate a new MercadoPago object, normally this can be binded to a container and used across the project
$mercadoPago = MercadoPago::load($config);
// These filters are an intended for reference, use it as you need it
$filters = ["external_reference" => "EXTERNAL_REFERENCE_TO_LOOK_FOR"];
$payments = $mercadoPago->searchPayments($filters);
?>

<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>

    <table>
        <?php 
foreach ($payments as $payment) {
    // $payment it's an instance of Payment Class, use the available methods in it.
    ?>
            <tr>
                <td><?php 
    echo $payment->id();
    ?>