Retrieving input value from view to controller in slim framework

Hello, I have the following difficulty: I have a field that the user fills in with the value of the cnpj, I need to retrieve this value for the controller, set this dynamic value in a query within a method to be able to fill in a select on another page referring to this cnpj in question. I do not program in the slim framework, I am trying to do it for days, I would like an example or a way to implement a solution according to this need.

// This is the input that I should get the value

<input type="tel" class="form-control numeric" name="cgc" id="cgc" placeholder="CPF / CNPJ">
// this is the query that i must fill in with the return of the typed cnpj

public function getDevolucoes($request, $response, $args) {

    $cnpj = $request->getParam('cgc');

    $devolucoes = $this->database->query('
    select  distinct
        dev_devolucoes.id_devolucao as cod_devolucao,
        dev_devolucoes.numeronf As nfvendaccgl,
        dev_devolucoes.numeronf_devolucao as nfdevolucaocliente,
        dev_itensdevolucao.quantidade_devolvida as quantidade
        itenscarregamento on itenspedido.iditenspedido = itenscarregamento.iditenspedido 
        pedido on itenspedido.idpedido = pedido.idpedido
        dev_devolucoes on itenscarregamento.numeronf = dev_devolucoes.numeronf
        dev_itensdevolucao on dev_devolucoes.id_devolucao = dev_itensdevolucao.id_devolucao
        pedido.cnpj =  :cgc AND 
        dev_devolucoes.dev_status = :devstatusId
    ', [
        ':devstatusId' => '6',
        ':cgc' => $cnpj

    $response = $response->withJson($devolucoes);
    $response = $response->withAddedHeader('cache-control', 'no-cache');
    $response = $response->withAddedHeader('pragma', 'no-cache');
    $response = $response->withAddedHeader('expires', '0');

    return $devolucoes;

Thank you for your suggestions.

If the request Content-Type is either application/x-www-form-urlencoded
or multipart/form-data, then you can retrieve all POST parameters as follows:

// Get all POST parameters
$parameters = $request->getParsedBody();

// Get a single POST parameter by key
$value = $parameters['foo'];