Create several file inputs for your form. The use of an array name image[] is one approach.
Image to upload: <input type="file" name="image[]" /><br />
Image to upload: <input type="file" name="image[]" /><br />
Image to upload: <input type="file" name="image[]" /><br />
.... // as many as you want. Just be aware of upload_max_filesize, memory_limit, post_max_size etc.
<br />
Next, include a for loop in your uploader.php file to enclose your file upload code.
for($i=0;$i<count($_FILES["image"]["name"]);$i++){
$fileData = pathinfo(basename($_FILES["image"]["name"][$i]));
...
if (move_uploaded_file($_FILES["image"]["tmp_name"][$i], $target_path))
{
...
echo "The image {$_FILES['image']['name'][$i]} was successfully uploaded and added to the gallery<br />";
}
else
{
echo "There was an error uploading the file {$_FILES['image']['name'][$i]}, please try again!<br />";
}
Then Remove the duplicate code above the for a loop. Remove basename(), as this is causing your extension to fail, and pathinfo() will return the ['basename'].