creo que algo asi seria :
Código PHP:
<?php
$guarda_url ='http://'.$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];?>
<form action="" method="post" enctype="multipart/form-data" name="uploadform">
<table width="350" border="0" cellpadding="1" cellspacing="1" class="box">
<tr>
<td width="246"><input type="hidden"
name="MAX_FILE_SIZE" value="2000000"><input name="userfile"
type="file" class="box" id="userfile">
</td>
<td width="80"><input name="upload" type="submit" class="box" id="upload" value=" Upload "></td>
</tr>
</table>
<input type="hidden" name="guarda_url" value="<?php echo $guarda_url;?>">
</form>
avisame si te ha servido
saludos!