Input validation and sanitization in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get user input from a POST request safely.

PHP

<?php
$user_input = $_POST[[1]];
?>

Drag options to blanks, or click blank then click option'

Ausername

B"username"

C"user_input"

Dinput

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the key causes a syntax error.

Using a wrong key name returns null.

The key to access POST data must be a string in quotes, like "username".

2fill in blank

medium

Complete the code to sanitize the user input as a string.

PHP

<?php
$clean_input = filter_var($user_input, [1]);
?>

Drag options to blanks, or click blank then click option'

AFILTER_SANITIZE_STRING

BFILTER_VALIDATE_EMAIL

CFILTER_SANITIZE_EMAIL

DFILTER_VALIDATE_INT

Attempts:

3 left

💡 Hint

Common Mistakes

Using validation filters instead of sanitization filters.

Choosing filters meant for emails or numbers.

FILTER_SANITIZE_STRING removes unwanted characters from strings.

3fill in blank

hard

Fix the error in the code to validate if input is an integer.

PHP

<?php
if (filter_var($input, [1]) === false) {
    echo "Invalid number.";
}
?>

Drag options to blanks, or click blank then click option'

AFILTER_VALIDATE_INT

BFILTER_SANITIZE_NUMBER_INT

CFILTER_VALIDATE_BOOLEAN

DFILTER_SANITIZE_STRING

Attempts:

3 left

💡 Hint

Common Mistakes

Using sanitization filters instead of validation filters.

Confusing boolean validation with integer validation.

FILTER_VALIDATE_INT checks if the input is a valid integer.

4fill in blank

hard

Fill both blanks to sanitize and then validate an email input.

PHP

<?php
$email = filter_var($raw_email, [1]);
if (filter_var($email, [2]) === false) {
    echo "Invalid email.";
}
?>

Drag options to blanks, or click blank then click option'

AFILTER_SANITIZE_EMAIL

BFILTER_VALIDATE_INT

CFILTER_VALIDATE_EMAIL

DFILTER_SANITIZE_STRING

Attempts:

3 left

💡 Hint

Common Mistakes

Validating before sanitizing.

Using wrong filters for email validation.

First sanitize the email, then validate it.

5fill in blank

hard

Fill all three blanks to create a sanitized array of usernames longer than 3 characters.

PHP

<?php
$usernames = ['alice', 'bob', 'eve123', 'jo'];
$filtered = array_filter(array_map(function($name) {
    return filter_var($name, [1]);
}, $usernames), function($name) {
    return strlen($name) [2] [3];
});
?>

Drag options to blanks, or click blank then click option'

AFILTER_SANITIZE_STRING

B>

C3

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using validation filters instead of sanitization.

Using wrong comparison operators or values.

Sanitize each username, then keep only those longer than 3 characters.