Extension of scenario 2 for synchronous batch uploads - in which you can dynamically setup the initialPreview and initialPreviewConfig immediately after upload at runtime. For this you must return the initialPreview, initialPreviewConfig, and append properties within a JSON object from your server. Refer to the documentation for receiving data on server or sending data from server in synchronous mode.

The example below contains an example of a PHP server code that can respond with such a JSON as mentioned above.

Code

<div class="file-loading">
    <input id="input-704" name="kartik-input-704[]" type="file" accept="image/*" multiple>
</div>

<script>
$(document).ready(function() {
    $("#input-704").fileinput({
        allowedFileExtensions: ['jpg', 'png', 'gif'],
        uploadUrl:  "/file-upload-batch/2",
        uploadAsync: false,
        overwriteInitial: false,
        minFileCount: 1,
        maxFileCount: 5,
        initialPreviewAsData: true // identify if you are sending preview data only and not the markup
    });
});
</script>

Server Code (PHP Example)

// example of a PHP server code that is called in `uploadUrl` above
// file-upload-batch script
header('Content-Type: application/json'); // set json response headers
$outData = upload(); // a function to upload the bootstrap-fileinput files
echo json_encode($outData); // return json data
exit(); // terminate

// main upload function used above
// upload the bootstrap-fileinput files
// returns associative array
function upload() {
    $preview = $config = $errors = [];
    $input = 'kartik-input-704'; // the input name for the fileinput plugin
    if (empty($_FILES[$input])) {
        return [];
    }
    $total = count($_FILES[$input]['name']); // multiple files
    $path = '/uploads/'; // your upload path
    for ($i = 0; $i < $total; $i++) {
        $tmpFilePath = $_FILES[$input]['tmp_name'][$i]; // the temp file path
        $fileName = $_FILES[$input]['name'][$i]; // the file name
        $fileSize = $_FILES[$input]['size'][$i]; // the file size
        
        //Make sure we have a file path
        if ($tmpFilePath != ""){
            //Setup our new file path
            $newFilePath = $path . $fileName;
            $newFileUrl = 'http://localhost/uploads/' . $fileName;
            
            //Upload the file into the new path
            if(move_uploaded_file($tmpFilePath, $newFilePath)) {
                $fileId = $fileName . $i; // some unique key to identify the file
                $preview[] = $newFileUrl;
                $config[] = [
                    'key' => $fileId,
                    'caption' => $fileName,
                    'size' => $fileSize,
                    'downloadUrl' => $newFileUrl, // the url to download the file
                    'url' => 'http://localhost/delete.php', // server api to delete the file based on key
                ];
            } else {
                $errors[] = $fileName;
            }
        } else {
            $errors[] = $fileName;
        }
    }
    $out = ['initialPreview' => $preview, 'initialPreviewConfig' => $config, 'initialPreviewAsData' => true];
    if (!empty($errors)) {
        $img = count($errors) === 1 ? 'file "' . $error[0]  . '" ' : 'files: "' . implode('", "', $errors) . '" ';
        $out['error'] = 'Oh snap! We could not upload the ' . $img . 'now. Please try again later.';
    }
    return $out;
}