This allows one to implement a chunked file uploader functionality with the aids of JavaScript class on the client/browser side and a PHP class on the server side. It is especially useful when you want to overcome the upload_max_filesize | post_max_size php.ini restriction.

To implement this functionality is straightforward:

• your main index.html file initializes a MyChunkUploader JavaScript object (see chunk-uploader.js) which you'll use it to start sending your file to the remote server. To do that you call the method upload_chunked ('/upload.php',FILE). This call splits the file into multiple chunks and sends them via a series of Ajax POST requests to the upload.php PHP script.
• the upload.php is merly a dispatcher (however, this is where you can inject your own logic before the server accepting the client requests); it receives the previous POST requests and forwards them to a MyChunkUploader PHP instance (see MyChunkUploader.php)
• the MyChunkUploader PHP instance saves each chunk to a temporary file; when all chunks are received the temporary/chunked files are concatenated resulting the final uploaded file which will be stored on a preset folder on the web server.

• front-end : IE10+, FF13+, Chrome10+, Opera12+
• back-end : PHP 5.3+, a web server with PHP support

This JavaScripts class (actually a function) allows you to split a client-side FILE into multiple chunks and to send these chunks asynchronously (thanks to AJAX) to your server PHP backend. The class is flexible, provides real-time feedback and progress.

The class_signature argument is used to prefix the following custom header names:

• Type : a header used to specify the file content-type
• Security-Nonce : a header used to specify the client security nonce
• Raw-Post : a header used to specify if the chunk is sent within a JSON object or as a raw binary data
• Abort : a header used to specify that the client requested to abort the whole process
• Timeout : a header used to specify the upload maximum allowed time

When the class_signature is not provided then X-MyChunkUploader is assumed by default.

options a JSON object with the following properties:

• max_chunk_size : the size in bytes of a chunk (default to 1048576 bytes)
• raw_post : when true the client will send the chunk as a raw binary data, otherwise the data will be encapsulated within a JSON object
• send_interval : the number of milliseconds to wait before creating and sending the next available chunk
• max_parallel_chunks : the number of chunks that may be created/sent at a time (the more parallel chunks are sent the more resources are used by the client/server systems)

The following events allow you to control the file progress and/or the upload state:

• on_chunk_start (object) : this function is called right after a new chunk is created. The JSON object contains the following arguments:

  • index : the index number assigned to the current started chunk
  • range : a JSON object having the following attributes:
    • from : the chunk start position
    • to : the chunk end position

• on_upload_progress (object) : this function is called while the file chunk is uploading. The JSON object contains the following arguments:

  • sent : the number of bytes sent so far
  • total : the total number of bytes of the file
  • percentage : the percentage of what is already sent
  • elapsed : the current elapsed time in seconds
  • eta : the remaining seconds to finish

  NOTE: you may use the Number.toHMS() prototype to format the seconds as HH:mm:ss

• on_ready (object) : this function is called once a chunk was successfully sent. The JSON object contains the following arguments:

  • sent : the number of bytes sent so far
  • total : the total number of bytes of the file
  • elapsed : the current elapsed time in seconds
  • file : the JS file object

• on_error (XHR,object,type) : this function is called in case of a AJAX/HTTP error. XHR is the XMLHttpRequest object used for the current request. The type is a string specifying the error type (normally server). The JSON object contains the following arguments:

  • success : false
  • json : a JSON object containing among other properties the name which is the file name. Other properties might be message and code containing the error message and the error code.

• on_abort (XHR, object) : this function is called after the abort() function was successfully acknowledged by the server. The XHR is a reference to the current XMLHttpRequest instance. The JSON object contains the following arguments:

  • success : false
  • message : Aborted by user
  • code : UI

• on_done (XHR,start_time) : this function is called when all the chunks were sent and the file is completely uploaded to the server. XHR is the XMLHttpRequest object used for the current request. The start_time is the timestamp (in milliseconds) when the upload was started.

The following methods may be used to upload a file to the server:

• upload_chunked (url, file, nonce, params) : call this function to start uploading a file to the server. The url parameter is the absolute|relative URL to the upload.php script. The file is the JS file object to be uploaded. Optionally you may send also a security nonce within the nonce argument. The MyChunkUploader PHP class implements a callback that allows you to validate the security nonce at the server level. The JSON params argument may contain any other parameters that you want to send to server.
• abort (params) : call this function to tell the server application that the upload is going to be aborted, thus to do its clean-up (remove all temporary uploaded chunks). The JSON params argument may contain any other parameters that you want to send to server. params example: For instance when I use this class in a WordPress plug-in I usually encapsulate the action and the nonce arguments within it. Please note that params is used only when options.raw_post = false.