PHP生成的表单不提交AJAX

I have a select with ROWID in the value and the name in the value,

<select name="opcoes"  onchange="showInfo(this.value)">
<option value=''>Select</option>
<option value=6>A</option>
<option value=2>F</option>
<option value=5>L</option>
<option value=1>M</option>
</select>

when you select one i have this ajax code to create a form with php,

    function showInfo(str)
{


if (str=="")
  {

  document.getElementById("fields").innerHTML="";
  return;
  } 
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
xmlhttp.onreadystatechange=function()
  {
  if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
    document.getElementById("fields").innerHTML=xmlhttp.responseText;
    }
  }
xmlhttp.open("GET","php/vendors/getRow.php?id="+str,true);
xmlhttp.send();
}

Next if the selected value isnt "" it goes to the php,

...conection to the database...

echo "<form action='/php/vendors/edit.php' onSubmit=\"return confirm('Deseja editar?')\" method='post' >"; 
echo "<td><input type='text' name='editname'   value='".utf8_encode($linha[vendor_name])."'    ></td>";
echo "<td><input type='text' name='editemail'    value='".utf8_encode($linha[vendor_email])."'    ></td>";
echo "<td><input type='text' name='editwebsite'    value='".utf8_encode($linha[vendor_website])."'  ></td>";
echo "<td><input type='text' name='editphone'    value='".utf8_encode($linha[vendor_phone])."'    ></td>";
echo "<td><input type='text' name='editfax'     value='".utf8_encode($linha[vendor_fax])."'     ></td>";
echo "<td><input type='text' name='editadress'    value='".utf8_encode($linha[vendor_adress])."'   ></td>";
echo "<td><input type='text' name='editincharge'   value='".utf8_encode($linha[vendor_incharge])."'  ></td>";
echo "<td class='btn'><input class='edit' type='submit' value=''></td>";
echo "</form>";

It displays every information correctly the ONLY problem is that it does not submit when i click the input submit button... any ideas why?