Where is the words in ' ' located? - php

Question

I am learning php, (absolute beginner) and want to know where the words in '' are located. I downloaded a code from online for a login system and am trying to learn how it works. Here is the code portion:
<?php
// any HTML input *must* be HTML-escaped to prevent the user from injecting malicious JavaScript code
function html_escape($raw_input, $encoding)
{
return htmlspecialchars($raw_input, ENT_QUOTES | ENT_SUBSTITUTE, $encoding);
}
/* Displays user information and some useful messages */
session_start();
if ($_SESSION['logged_in'] != 1) {
$first_name = 'Guest, Please Login or Sign Up to Play!';
$last_name = '';
}
else {
// Makes it easier to read
$first_name = $_SESSION['first_name'];
$last_name = $_SESSION['last_name'];
}
?>
So where it says, "if ($_SESSION['logged_in'] != 1) {", when it says logged_in, where would that be defined? Is it defined in another file with the $logged_in, or what?
Also, i found some file where it says "$_SESSION['logged_in'] = true;" but i don't know if it means something, if it does please tell me!
Thanks so much.
(i'm a beginner so go easy on me please)

Answer 1

You can store data in $_SESSION variables after session_start(); and assign values to it with:
$_SESSION['keyname'] = 'value';
You can write apostrophe (') or double quote (") to save string variables.
More informations here: http://php.net/manual/de/reserved.variables.session.php
Your code if ($_SESSION['logged_in'] != 1) is just a boolean check if $_SESSION['logged_in'] is set to 1 (true) or 0 (false).
So it checks your $_SESSION array with the key logged_in if 1 is set or not.
I hope I could help you with that?

Answer 2

In the code you shown, this is the check login step in login process. In login process, there is two step we need to do:
Check login: determine that current session is logged in or not. If not, shown/redirect to login page.
Login page: is used to input username & password and check inputed value. If username & password is correct, we save a value to $_SESSION to flag this user is logged in.
To find how the $_SESSION['logged_in'] is set, you must find in your downloaded code the check login section.
In general this can be simple as:
if ($_POST['username'] == 'abc' && $_POST['password'] == 'xyz') {
$_SESSION['logged_in'] = 1;
// some code to refresh or redirect to main content
}
I hope this will help you!

Answer 3

Assume you have form with field 'username' and 'password' at HTML:
<form action='login.php' method='post'>
<input type='text' name='username'>
<input type='password' name='password'>
<input type='submit' value='Login'>
</form>
after clicking 'Login' button you will run login.php:
<?php
$allowedUser = 'johnny';
$allowedPass = 'mypassword';
session_start();
if (($_POST['username']!= '') && ($_POST['password'] !=''))
{
if (($_POST['username'] == $allowedUser) && ($_POST['username'] == $allowedPass))
$_SESSION['is_loged'] = 1; // session variable will be set when you have allowed credentials
}
?>