PHP script to download file

please i need a php script to download file from a folder in WAMPSERVER, i have a script to upload file which is working properly but when i upload i want to also download file.

this is my upoad script

<?php // display file upload form
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if (!isset($_POST['submit'])) { ?>
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<form enctype="multipart/form-data" action="<?php echo $_SERVER['PHP_SELF']?>" method="post">
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<input type="hidden" name="MAX_FILE_SIZE" value="8000000" /> Select file:
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<input type="file" name="data" />
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<input type="submit" name="submit" value="Upload File" /></form>
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<?php
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} else {
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// check uploaded file size
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if ($_FILES['data']['size'] == 0) {
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die("ERROR: Zero byte file upload");
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}
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// check if file type is allowed (optional)
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$allowedFileTypes = array("image/gif", "image/jpeg", "image/pjpeg");
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if (!in_array($_FILES['data']['type'], $allowedFileTypes)) {
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die("ERROR: File type not permitted");
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} // check if this is a valid upload
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if (!is_uploaded_file($_FILES['data']['tmp_name'])) {
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die("ERROR: Not a valid file upload"); } // set the name of the target directory
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$uploadDir = "./uploads/"; // copy the uploaded file to the directory
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move_uploaded_file($_FILES['data']['tmp_name'], $uploadDir . $_FILES['data']['name']) or die("Cannot copy uploaded file"); // display success message
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echo "File successfully uploaded to " . $uploadDir .$_FILES['data']['name']; } ?>

please can any one help me with code to download the files that have been uploaded.