When a user clicks a link it uses jquery ajax to submit a form to go to paypal. Not working for some reason. Really appreciate any help...

LINK TO CLICK

I put this in an href for onClick:

javascript:go_paypal();

CODE TO EXECUTE ON CLICK

    function go_paypal() {

data = 'req_paypal=1';

$.blockUI({ message: '<h1> Going to Paypal...</h1>',css:{background:'#000'} });
    $.ajax({
      type: "POST",
      url: "index.php",
      data: data,
      success: function(data) { $("#paypal_form").html(data); $("#payPalForm").submit(); } ,
      error: function() {$.unblockUI(); alert('Unable to communicate to server.'); }
    }); 
    return false;

}

CODE TO GO ON SUBMIT

if(isset($_POST['req_paypal']) && $_POST['req_paypal'] == 1 ) {


    $sql = 'INSERT INTO `transactions` (id,type,ip,time,ammount,status) VALUES (NULL,1,\''.$_SERVER['REMOTE_ADDR'].'\',\''.time().'\',\''.$global['paypal_prod_amount'].'\',0) ';
    echo $sql;

    mysql_query($sql);

    $id = mysql_insert_id();

    $html = '
    <form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post" id="payPalForm">
<input type="hidden" name="item_number" value="One Year of Imgur Pro">
<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="no_note" value="1">
<input type="hidden" name="business" value="'.$global['paypal_email'].'">
<input type="hidden" name="custom" value="'.base64_encode($id).'">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="return" value="'.$global['paypal_return'].'">
<input name="item_name" type="hidden" id="item_name" value="One Year of Imgur Pro" >
<input name="amount" type="hidden" id="amount" value="'.$global['paypal_prod_amount'].'" >
</form>
    ';

    echo $html;exit;
}