CS310 Quiz 2 Solution and Discussion

[zaasmi]

said in CS310 Quiz 2 Solution and Discussion:

How will we retrieve the value of session variable set in the following PHP code?

Retrieve session variable
Answer: (d) $_SESSION[“color”];$
The session variable is stored in the superglobal array $_SESSION with the key “color”. To retrieve its value, you must access this specific array using the same key. The other options use incorrect array names or incorrect keys.

To retrieve a session variable in PHP, you access the $_SESSION superglobal array using the specific key (name) that was used to set it.

The Syntax

If your session variable was set like this:
$_SESSION['username'] = "Alex";

You retrieve it like this:

echo $_SESSION['username'];

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Important Steps for Retrieval

For the value to be accessible, you must follow these two rules:

1. Start the Session: You must call session_start(); at the very top of your PHP file before trying to access the $_SESSION array.
2. Check if it Exists: It is best practice to use isset() to avoid an “Undefined index” error in case the session has expired or wasn’t set.

Example Code:

<?php
session_start(); // Mandatory to access session data

if(isset($_SESSION['username'])) {
    echo "Welcome back, " . $_SESSION['username'];
} else {
    echo "User is not logged in.";
}
?>

Summary of Session Functions

Action	PHP Command
Start/Resume	session_start();
Set/Retrieve	$_SESSION['key']
Remove one variable	unset($_SESSION['key']);
Destroy all data	session_destroy();

Would you like me to show you the specific code to set a session variable first, or perhaps how to destroy a session when a user logs out?

[zaasmi]

said in CS310 Quiz 2 Solution and Discussion:

Which of the following PHP syntax is used to remove all HTML tags from a string? CS310

To remove all HTML tags from a string in PHP, you use the filter_var() function with the FILTER_SANITIZE_STRING constant or the strip_tags() function.

1. Using filter_var() (Standard for sanitization)

This is the modern approach for cleaning input data.

$input = "<h1>Hello</h1> <p>World!</p>";
$clean = filter_var($input, FILTER_SANITIZE_STRING);
// Result: "Hello World!"

Note: As of PHP 8.1.0, FILTER_SANITIZE_STRING is deprecated. While still common in exam questions (like CS310), the modern replacement is htmlspecialchars() or strip_tags().

2. Using strip_tags() (Dedicated function)

This is a very common and straightforward function specifically designed to strip HTML and PHP tags from a string.

$input = "<b>Bold Text</b>";
echo strip_tags($input); 
// Result: "Bold Text"

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Comparison of Methods

Method	Best Use Case	Key Feature
strip_tags()	General purpose stripping	Allows you to specify “allowable tags” that should NOT be removed.
filter_var()	Data sanitization pipelines	Part of a unified filtering system for emails, URLs, and integers.
htmlspecialchars()	Security (XSS prevention)	Doesn’t remove tags, but converts them to plain text so the browser won’t execute them.

Would you like me to show you how to use strip_tags() while keeping certain tags (like <b> or <i>) intact?

[zaasmi]

said in CS310 Quiz 2 Solution and Discussion:

If we want to show all the session variable values for a user session then following code will be used.

To see every variable currently stored in a user’s session, you use the print_r() or var_dump() function on the $_SESSION superglobal.

These functions allow you to output the entire contents of the associative array in a readable format, which is extremely helpful for debugging.

The Code

<?php
session_start(); // You must always start the session first

// Option 1: Using print_r (Cleanest for reading)
echo "<pre>";
print_r($_SESSION);
echo "</pre>";

// Option 2: Using var_dump (Provides more detail like data types)
var_dump($_SESSION);
?>

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Why use <pre>?

When using print_r() or var_dump(), wrapping the code in HTML <pre> (preformatted text) tags is a “pro-tip.” It forces the browser to display the array with proper indentation and line breaks, making it much easier for you to read than a single long line of text.

Common Session Commands Summary

Purpose	Command
Start/Resume	session_start();
Show All Values	print_r($_SESSION);
Check if a variable exists	isset($_SESSION['key']);
Clear all values	session_unset();

Would you like me to show you how to loop through the session variables using a foreach loop if you want to format the output as a list?