Starting file download with Javascript

Ever wondered how many sites triggers download after a given timeinterval or by pressing a button or clicking a link.
In this tutorial I'm going to show you how to various methods initiate downloads from your website.

1. Simple Old Method :

   This is the simpleset method to start download, just create a <a> and point it to your file location.

    
   <a href="file.ext" > Click Here <a> To Download
   

2. Javascript based download

   We can use a simple javascript to start file download. We will use window.location method to initiate the download.
   HTML code :

    
   <input type="button" value="Download" onClick="download('file.ext')" >
   

   
   JavaScript Code:

    
   <script>
   function download(file)
   {
    window.location=file;
   }
   </script>
   

3. Download using javascript and Iframe

   <iframe id="frame" style="display:none"></iframe>
   <a href="javascript:download('file.ext')">download</a>
   

   <script type="text/javascript">
   function download(path) 
   {
       var ifrm = document.getElementById("frame");
       ifrm.src = path;
   }
   </script>
   

4. Download using Javascript, Iframe and PHP

   Create a Link :

   <iframe id="frame" style="display:none"></iframe>
   <a href="javascript:download('file.ext')">download</a>
   

   Javascript:

   <script type="text/javascript">
   function download(path) 
   {
       var ifrm = document.getElementById(frame);
       ifrm.src = "download.php?path="+path;
   }
   </script>
   

   Code for download.php file :

   <?php 
      header("Content-Type: application/octet-stream");
      header("Content-Disposition: attachment; filename=".$_GET['path']);
      readfile($_GET['path']);
   ?>
   

5. Javascript based download with timer

   Above method can be used to start a javascript based timer and at the end of timer download will start.
   Simply put the code in file and it will start the timer.
   After time is up we can either display link or directly start download.
   You can use all of above method with the timer with few changes. HTML code:

    
   <div id="counter-text"> Please Wait For <span id="counter">  </span> Seconds. 
   </div>
   <a href="javascript:download('file.ext')" style="display:none" id="link"> 
   Click To Download </a>
   

   JavaScript Code:

    
   <script>
   time = 5;
   document.getElementById("counter").innerHTML = time;
   timer = setInterval("count()",1000);
   
   function count()
   {
    if(time == 1)
    {
     //Cleare Timer and remove counter from page
     clearInterval(timer);
     document.getElementById("counter-text").style.display="none";
     //If you want to display link
     document.getElementById("link").style.display="block";
     //Or directly start download
     //download('file.ext');
    }
    else
    {
     time--;
     document.getElementById("counter").innerHTML = time;
    }
   }
   function download(file)
   {
    window.location=file;
   }
   </script>
   

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Related Posts :

• Submitting and Securing the form data with Javascript
• Using HTML5 Web Worker: Introducing Multithreading in JavaScript

PHP MySQLI Tutorial

What is MySQLI :

The MySQLi Extension (MySQL Improved) is a relational database driver used in the PHP programming language to provide an interface with MySQL databases.
MySQLi is an improved version of the older PHP MySQL driver, offering various benefits.
The developers of the PHP programming language recommend using MySQLi when dealing with MySQL server versions 4.1.3 and newer (takes advantage of new functionality).

Why Mysqli :

The MySQLi extension provides various benefits with respect to its predecessor, the most prominent of which are:

• An object-oriented interface
• Support for prepared statements
• Support for multiple statements
• Support for transactions
• Enhanced debugging support
• Embedded server support

MySQLi Vs MySQL

	MySQLi	MySQL
PHP version introduced	5.0	Prior to 3.0
Included with PHP 5.x	yes	Yes
MySQL development status	Active development	Maintenance only
Recommended by MySQL for new projects	Yes - preferred option	No
API supports Charsets	Yes	No
API supports server-side Prepared Statements	Yes	No
API supports Stored Procedures	Yes	No
API supports Multiple Statements	Yes	No
Supports all MySQL 4.1+ functionality	Yes	No

Here is a simple code that implements mysqli

<?php


 //CONNECT TO THE DATABASE
 $DB_HOST = 'HOST';
 $DB_USER = 'USERNAME';
 $DB_PASS = 'PASSWORD';
 $DB_NAME = "mysqlitest";

 $mysqli = new mysqli($DB_HOST, $DB_USER, $DB_PASS, $DB_NAME);
 
 
 if (mysqli_connect_errno()) {
  printf("Connect failed: %s\n", mysqli_connect_error());
  exit();
 }

 //CREATE TABLE
 $q = "CREATE TABLE user (id int AUTO_INCREMENT PRIMARY KEY, 
     name varchar(30))";
 $mysqli->query($q);
 
 //INSERT FEW VALUES
 $q = "INSERT INTO user VALUES (NULL, 'abc')";
 $mysqli->query($q);
 $q = "INSERT INTO user VALUES (NULL, 'bcd')";
 $mysqli->query($q);
 $q = "INSERT INTO user VALUES (NULL, 'xyz')";
 $mysqli->query($q);
 
 
 //SELECT A USER
 $q = "SELECT * FROM user WHERE id=3";
 $result = $mysqli->query($q) or die($mysqli->error.__LINE__);

 // GOING THROUGH THE DATA
 if($result->num_rows > 0) {
  while($row = $result->fetch_assoc()) {
   echo $row['name']; 
  }
 }
 else {
  echo 'NO RESULTS'; 
 }
 // CLOSE CONNECTION
 mysqli_close($mysqli);
?>

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How to upload file to server in android

If you are building an app that requires files to be uploaded on server you will need to follow this method. By using this method,  you will be able to upload a file from your SD Card.

We will be using httpmime-4.2.5.jar for this tutorial. You can download it from here. Extract the zip file and you will find jar file under lib folder.

1. Create a new android project in Eclipse, and add the jar file to lib folder.
2. Add android.permission.INTERNET and android.permission.WRITE_EXTERNAL_STORAGE in your manifest file.
3. Use the following code :

 String address;
 MultipartEntity entity;
 File f;
 FileBody fb;
 entity = new MultipartEntity(
    HttpMultipartMode.BROWSER_COMPATIBLE);
 address = Environment.getExternalStorageDirectory()
    + "/temp.dat";
 f = new File(address);
 fb = new FileBody(f, "application/octect-stream");
 entity.addPart("file", fb);
 HttpClient httpclient = new DefaultHttpClient();
 HttpPost httppost = new HttpPost("Your URL Here");
 
 httppost.setEntity(entity);
 HttpResponse response = httpclient.execute(httppost);
 BufferedReader bufferedReader = new BufferedReader(
  new InputStreamReader(
   response.getEntity().getContent()));
 StringBuffer stringBuffer = new StringBuffer("");
 String line = "";
 String LineSeparator = System.getProperty("line.separator");
 while ((line = bufferedReader.readLine()) != null) {
  stringBuffer.append(line + LineSeparator);
 }
 bufferedReader.close();
 return stringBuffer.toString();
 } catch (ClientProtocolException e) {
  return e.toString();
 } catch (IOException e) {
  return e.toString();
 } 

Here we use MultipartEntity from the http library to add file for uploading.

f = new File(address);

fb = new FileBody(f, "application/octect-stream");
entity.addPart("file", fb);

We select the file given by address and then we get filebody using the FileBody Class and then add it to the entity.

HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("Your URL Here");
httppost.setEntity(entity);
HttpResponse response = httpclient.execute(httppost);

We create a new HttpClient and a HttpPost object, set entity and execute the reuqest.
Now android does not allow us to use network operations under the main thread, either we have to create a new thread or we use AsyncTask. You can Find the full source code here or download it here .

You can also use FTP library to uplaod the file which is better than this approach as described here.

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