to help troubleshoot, try adding the following code at line 1 to turn on error reporting:
change the following line:
$WA_redirectURL = "slike_Results.php";
$WA_redirectURL = "";
so that it will no longer redirect.
go to the bindings panel and expand the WA Uploaded Files section add the debug info binding to the page just before the closing the </body> tag.
also add this code just before the closing </body> tag:
<pre><?php var_dump($_POST); ?></pre>
<pre><?php var_dump($_FILES); ?></pre>
and try uploading a file that failed before, this might give us some information to go on.