$_POST['probleem'] in Internet explorer

    <form action="<?php echo $_SERVER['REQUEST_URI'];?>" id="zoekform" method="post">
      <div>
        <input name="pc"    id="pc" type="text" />
        <input name="radio" id="particulier" type="radio"  value="0" checked="checked" />
        <input name="radio" id="zakelijk" type="radio"  value="1" />
        <input type="image" id="goBtn" name="goBtn"  src="images/goBtn.png" value="zoek"  />
      </div>
    </form>

<form action="<?php echo $_SERVER['REQUEST_URI'];?>" id="zoekform" method="post">
      <div>
        <input name="pc"    id="pc" type="text" />
        <input name="radio" id="particulier" type="radio"  value="0" checked="checked" />
        <input name="radio" id="zakelijk" type="radio"  value="1" />
        <input type="image" id="goBtn" name="goBtn"  src="images/goBtn.png" value="zoek"  />
      </div>
    </form>

<?php
if(isset($_POST['goBtn']) || isset($_POST['goBtn_x']))
{
   //meuk

<?php
if(isset($_POST['goBtn']) || isset($_POST['goBtn_x']))
{
   //meuk

<form action="/" id="zoekform" method="post">

<form action="/" id="zoekform" method="post">

<form action="/index.php" id="zoekform" method="post">

<form action="/index.php" id="zoekform" method="post">