Curious Problem with $_POST

I have a form for uploading files. It is intended to upload photos. I have it listed at the end. When I upload a jpg everything is fine. The $_POST variable is populated as expected. If I upload a zip file, it is empty! print_r ($_POST); gives Array ( ) If I upload a jpg Print_r gives: Array ( [form] => uploadimagesform [MAX_FILE_SIZE] => 100000 [category] => 1 [photo_caption] => Array ( [0] => [1] => [2] => [3] => ) [submit] => Add Photos ) I am at a total loss to understand this, and don't know where to begin. Help! Thanks in advance Stephen <form enctype="multipart/form-data" action="up.php" method="post" name="upload_form"><br /> <input name="form" type="hidden" value="uploadimagesform" /> <label for="category">Select Category</label> <select id="category" name="category">

       <option value=1>Name</option>
       <option value=2>Purple</option>

</select><br /><br /> <label for="Photo1">Photo 1:</label> <input id="photo_filename[]" name="photo_filename[]" type="file" /><br /> <label for="Caption1">Caption: </label> <textarea id="photo_caption[]" name="photo_caption[]"></textarea><br

/><br />         <label for="Photo2">Photo 2:</label>
   <input id="photo_filename[]" name="photo_filename[]" type="file" /><br />

<label for="Caption2">Caption: </label> <textarea id="photo_caption[]" name="photo_caption[]"></textarea><br

/><br />          <label for="Photo3">Photo 3:</label>
   <input id="photo_filename[]" name="photo_filename[]" type="file" /><br />

<label for="Caption3">Caption: </label> <textarea id="photo_caption[]" name="photo_caption[]"></textarea><br

/><br />         <label for="Photo4">Photo 4:</label>
   <input id="photo_filename[]" name="photo_filename[]" type="file" /><br />

<label for="Caption4">Caption: </label> <textarea id="photo_caption[]" name="photo_caption[]"></textarea><br

/><br />         <input type="submit" name="submit" value="Add Photos" />

</form>