Uploading files from a formData

I am sending via ajax a formData. But, what is arriving as a request parameter, is an empty string. And another question, is this form of uploading correct?

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 $anexo = Yii::$app->request->post('AnexoDocumento');
        if(!empty($anexo['foto_url']) || !empty($anexo['arquivo_url'])){

            $modelArquivo = new AnexoDocumento();
            $modelArquivo->load(Yii::$app->request->post());

            $imagem = UploadedFile::getInstance($modelArquivo, 'foto_url');

            $doc = UploadedFile::getInstance($modelArquivo, 'arquivo_url');


            if($imagem){
                $fecha = date('YmdHms');
                $result = $imagem->saveAs('@web/images/outrosDoc/'.$fecha.'_'.$modelArquivo->arquivo_url, false);
                $imagem->arquivo_url = $result->get('ObjectURL');
            }

            if($doc){
                $fecha = date('YmdHms');
                $result = $doc->saveAs('@web/images/doc/'.$fecha.'_'.$modelArquivo->foto_url, false);
                $doc->url = $result->get('ObjectURL');
            }

            $modelArquivo->member_id = $model->id;
            $modelArquivo->save(false);
        }

How are you collecting data in javascript and how are you performing the ajax call?
Can you share some more code?

function salveUser(){
'use strict';

var form = $('#form_basico');
var formData = new FormData(form[0]);
var id = $('#form_basico #user-id').val();
var ajaxUrl =  $('#saveDiv').data('url');


if(id != ''){
    ajaxUrl = ajaxUrl+'?id='+id;
}

var me = $(this);

if($('#user-cpf').val() != ''){
    if ( me.data('requestRunning') ) {
        return;
    }
    me.data('requestRunning', true);

    $.ajax({
        method: 'POST',
        url: ajaxUrl,
        data: formData,
        beforeSend: function () {
            form.addClass('sw-loading');
        },
        complete: function() {
            me.data('requestRunning', false);
        },
        contentType: false,
        processData: false,
    }).then(function (response) {
        var retorno = JSON.parse(response);
        form.removeClass('sw-loading');
        form.html(retorno.content);
        if (retorno.status === 200) {
            $.toast({
                heading: "Adicionado com sucesso",
                text: "Todas as informações foram registradas.",
                position: "top-right",
                loaderBg: "#ff6849",
                icon: "success",
                hideAfter: 2000,
            });
        }
        setTimeout(function(){
           // window.location.href = '../user/index';
        }, 3000);
    });
}else{
    $.toast({
        heading: "ATENÇÃO",
        text: "Campo CPF é obrigatório",
        position: "top-right",
        loaderBg: "#ff6849",
        icon: "warning",
        hideAfter: 2000,
    });
}
}