Isset, empty, and is_null behavior in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the variable $var is set.

PHP

<?php
$var = 5;
if ([1]($var)) {
    echo "Variable is set.";
} else {
    echo "Variable is not set.";
}
?>

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

Adefined

Bempty

Cisset

Dis_null

Attempts:

3 left

💡 Hint

Common Mistakes

Using empty() instead of isset() which also checks for empty values.

Using is_null() which only checks if a variable is null, but does not check if it is set.

The isset() function checks if a variable is set and is not null.

2fill in blank

medium

Complete the code to check if the variable $var is empty.

PHP

<?php
$var = 0;
if ([1]($var)) {
    echo "Variable is empty.";
} else {
    echo "Variable is not empty.";
}
?>

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

Astrlen

Bisset

Cis_null

Dempty

Attempts:

3 left

💡 Hint

Common Mistakes

Using isset() which returns true even if the variable is 0 or empty string.

Using is_null() which only checks if the variable is null.

The empty() function checks if a variable is empty. It returns true for values like 0, '', null, false, and empty arrays.

3fill in blank

hard

Fix the error in the code to correctly check if $var is null.

PHP

<?php
$var = null;
if ([1]($var)) {
    echo "Variable is null.";
} else {
    echo "Variable is not null.";
}
?>

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

Ais_null

Bempty

Cisset

Ddefined

Attempts:

3 left

💡 Hint

Common Mistakes

Using isset() which returns false if variable is null but does not check for null explicitly.

Using empty() which returns true for many values, not just null.

The is_null() function checks if a variable is exactly null.

4fill in blank

hard

Fill both blanks to include only words with length greater than 3 in the associative array.

PHP

<?php
$words = ['apple', 'cat', 'dog', 'banana'];
$result = [];
foreach ($words as $word) {
    if ([1]($word) [2] 3) {
        $result[$word] = strlen($word);
    }
}
print_r($result);
?>

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

Astrlen

B<

C>

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using count() which works for arrays, not strings.

Using '<' instead of '>' which would select shorter words.

Use strlen() to get the length of the word and check if it is greater than 3.

5fill in blank

hard

Fill all three blanks to create an array filtering code that keeps only non-empty, set, and non-null values.

PHP

<?php
$values = [0, null, '', 'hello', false, 42];
$result = [];
foreach ($values as $val) {
    if (![1]($val) && [2]($val) && ![3]($val)) {
        $result[] = $val;
    }
}
print_r($result);
?>

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

Aempty

Bisset

Cis_null

Dis_string

Attempts:

3 left

💡 Hint

Common Mistakes

Using is_null() directly in the condition without negation.

Using is_string() which is unrelated to emptiness or being set.

The code filters values that are not empty and are set. The empty() function checks for empty values, isset() checks if variable is set, and is_null() can be used to check for null values if needed.