Edit in JSFiddle

/* need JQuery */

/* function to redirect a webpage to another using post method */

function redirect_by_post(purl, pparameters, in_new_tab) {
    pparameters = (typeof pparameters == 'undefined') ? {} : pparameters;
    in_new_tab = (typeof in_new_tab == 'undefined') ? true : in_new_tab;

    var form = document.createElement("form");
    $(form).attr("id", "reg-form").attr("name", "reg-form").attr("action", purl).attr("method", "post").attr("enctype", "multipart/form-data");
    if (in_new_tab) {
        $(form).attr("target", "_blank");
    }
    $.each(pparameters, function(key) {
        $(form).append('<input type="text" name="' + key + '" value="' + this + '" />');
    });
    document.body.appendChild(form);
    form.submit();
    document.body.removeChild(form);

    return false;
}

$('#btn').button().click(function() {
    redirect_by_post('http://pamppi.info/jotform-testing/thankyou/postvars.php', {
        variable1: 'Carlos',
        variable2: 'Garcia'
    }, true);
});

<div class='ui-state-highlight ui-corner-all'> 
   in the server there is only a <br/> <br/>  < ? php print_r($_POST) ? >
   <br/> <br/> 
   So you can send any variables
</div>

<button id="btn">go an check the variables sent by post</button>

.ui-state-highlight {width:200px;margin:20px; padding:20px;}