Creating a ToDo webapp using PHP , MySQL and AJAX

I was trying to create a ToDo app just to improve my understanding the way Ajax is used with PHP and MySQL. Finally I have written this app, which is hosted at github. This blog post will serve as a tutorial for the same.


The database

`task_id` int(11) NOT NULL AUTO_INCREMENT,
`task` varchar(100) NOT NULL,
`target_date` date NOT NULL,
PRIMARY KEY (`task_id`)

Now we will create 5 files for the application.

  1. connect_db.php  – To connect with the database.
  2. create.php – The file used to create create the task. This will be called on submit of the form.
  3. create_task.php  – The file to show the form that will be used to create the task.
  4. delete.php – The file will be called when the delete action will be invoked.
  5. index.php  – The main container of the app which will show all the data.
  6. read.php  – The action to fetch all the data from the database.
  7. script.js – The JS file which will have all the actions using ajax.
  8. update.php – The action to update the data using edit action.
  9. update_form.php – The form to update the data.




In our index file , we are using the following ID which is used to display the data. All the page content will be dynamically loaded in the following div.

<div id="pageContent">



Also we have created two buttons which will be used to generate the list of tasks or add a new task

<button type="button" id="viewTasks">Check Tasks</button>

<button type="button" id="addTask">Add Task</button>


We can use the following code to connect with the database. This file will be included everytime we want to interact with the database.


try {
  # MySQL with PDO_MYSQL
  $DBH = new PDO("mysql:host=$host;dbname=$dbname", $user, $pass);
catch(PDOException $e) {
    echo $e->getMessage();

In script.js we will add the following code. This code will fetch the data dynamically from the database using the output from the read.php file. Similarly we will call all other files dynamically for the respective actions.

// READ Tasks
function showTasks(){
    // read and show the records after at least a second
    // we use setTimeout just to show the image loading effect when you have a very fast server
    // otherwise, you can just do: $('#pageContent').load('read.php', function(){ $('#loaderImage').hide(); });
    // THIS also hides the loader image
    setTimeout("$('#pageContent').load('read.php', function(){ $('#loaderImage').hide(); });", 1000);

Fork it at –

When to use GET and when to use POST

According to the HTTP specification, you should use the POST method when you’re using the form to change the state of something on the server end. For example, if a page has a form to allow users to add their own comments, like this page here, the form should use POST. If you click “Reload” or “Refresh” on a page that you reached through a POST, it’s almost always an error — you shouldn’t be posting the same comment twice — which is why these pages aren’t bookmarked or cached.

You should use the GET method when your form is, well, getting something off the server and not actually changing anything.  For example, the form for a search engine should use GET, since searching a Web site should not be changing anything that the client might care about, and bookmarking or caching the results of a search-engine query is just as useful as bookmarking or caching a static HTML page.

Also, don’t ever use GET method in a form that capture passwords and other things that are meant to be hidden.


Source –