Directory problem in XAMPP

My XAMPP (local host) server has the documents of a project in / htmdocs / project , inside it has index.html that calls This JavaScript / Jquery Code

$(document).ready(function () {$('#emailForm').submit(function(){
    $.ajax({
        type: 'POST',
        url: '/email.php',
        async: true,
        data: 'email=' + $('#campoEmail').val(),
        success: function() {alert("Sucesso")}
        //beforeSend: function() { alert("Enviando")}
    });
});

});

Form HTML

<form id="emailForm" >
        <input id="campoEmail" class="input-center" placeholder="Digite aqui" type="email" name="email" required="true">
        </br>
        </br>
        <input id="enviar" type="submit">
      </form>
    </div>

My question

What directory should the email.php file be in XAMPP to run when the JS file calls?