PHP - $_POST and $_SESSION

Question

What's the differences between $_POST and $_SESSION? When should I use each of them? I've been searching on internet, but I still don't understand. Please give simple explanation and give an example. Thanks

Maybe, this link can help you to explain the difference

Solution 1

In a nutshell, $_POST is a special array that stores data received from an HTTP POST request to a particular webpage. When the script loads, the raw HTTP POST data string is parsed and added to the $_POST array, so that it's easier for developers to use for common tasks, like handling HTML form submissions.

Example:

Raw HTTP data string format:
    key1=2&key2=3

$_POST array data format:
    $_POST = array('key1' => '2', 'key2' => '3');

$_SESSION data is not dependent on a particular page or HTTP request; its data is persisted across pages and is typically used for things like keeping track of account data while a user is logged-in. $_SESSION data is often stored in files on the server (or in a distributed storage mechanism like Redis) until it is either manually cleared (e.g., session_destroy()), or until PHP's garbage collection runs and destroys it.

Solution 2

Sample usages

$_POST

<?php
    // Access the username field with $_POST
    $username = $_POST['username'];

    // Output the username value
    echo $username;

    // If GET uncomment this
    // $username = $_GET['username'];
    // echo $username;

    // Or you can use $_REQUEST if you're in doubt about $_POST or $_GET
    // $username = $_REQUEST['username'];
    // echo $username;
?>

<form action="/" method="post"> <!-- You can change this as POST or GET -->
    <input type="text" name="username" />
    <input type="submit" value="Submit" />
</form>

By using $_POST, the address will be

http://domain.com/login

By using $_GET,

http://domain.com/login?username=somevalue

NOTE: $_GET displays the submitted value while $_POST don't

$_SESSION

<?php
    // You should call this first
    session_start();

    // Initialize the session value
    $_SESSION['mysession'] = 'hello_world';

    // Output the session value
    echo $_SESSION['mysession'];
?>

Comments

[Mike]

You've been searching on the internet? What have you found so far? The fact that you are confusing these makes me think you haven't actually searched for them at all. $_POST (or $_GET) are sent by the user to your script. $_SESSION is used to have your script remember different values between requests and is populated using the script itself, not directly by the user. I don't know what else you want to know.

[Grace Michelle]

@Mike I've been searching for that! How about the $_POST? And give an example

[Mike]

See also: php.net/manual/en/features.sessions.php, php.net/manual/en/reserved.variables.post.php and php.net/manual/en/language.variables.superglobals.php

[Mike]

Give an example of what? What are you trying to do?

[Julie Pelletier]

@GraceMichelle: He actually answered you very well. You should keep looking at tutorials.

[Grace Michelle]

So, if I want user to login to something, I better use $_SESSION?

[Mike]

@GraceMichelle You would need to use both. $_POST to get the username and password from the user and do your validation. $_SESSION to remember that the user is already logged in so that when they go to another page they don't have to keep re-entering their username and password.

[badandyomega]

If you want to retain information about their log-in and have access to it after the script terminates, yes. If you are handling the form submission data with their username and password, you'd use $_POST.

[gannagainz]

Why is it that if a form's method is "post", I can access the form's data using $_GET[] and using $_POST[]?