Array chunk and pad in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to split the array into chunks of size 2.

PHP

<?php
$numbers = [1, 2, 3, 4, 5];
$chunks = array_chunk($numbers, [1]);
print_r($chunks);
?>

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

A2

B3

C4

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 3 instead of 2 will create chunks of size 3.

Using 1 will create chunks of single elements.

The array_chunk function splits the array into smaller arrays of the given size. Here, size 2 means each chunk has 2 elements.

2fill in blank

medium

Complete the code to pad the last chunk to size 3 with zeros.

PHP

<?php
$numbers = [1, 2, 3, 4, 5];
$chunks = array_chunk($numbers, 3);
$last_chunk = $chunks[array_key_last($chunks)];
$padded = array_pad($last_chunk, [1], 0);
print_r($padded);
?>

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

A2

B3

C4

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Padding to 2 will not add enough elements.

Padding to 5 adds unnecessary zeros.

The array_pad function pads the array to the specified length. Here, padding to 3 adds zeros if the last chunk has fewer than 3 elements.

3fill in blank

hard

Fix the error in the code to pad the array to length 6 with -1.

PHP

<?php
$arr = [1, 2, 3];
$padded = array_pad($arr, [1], -1);
print_r($padded);
?>

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

A6

B3

C2

D4

Attempts:

3 left

💡 Hint

Common Mistakes

Using 3 or less does not add padding.

Using 4 pads but not to the desired length 6.

To pad the array to length 6, the second argument of array_pad must be 6.

4fill in blank

hard

Fill both blanks to create chunks of size 2 and pad each chunk to size 3 with 0.

PHP

<?php
$numbers = [1, 2, 3, 4, 5];
$chunks = array_chunk($numbers, [1]);
foreach ($chunks as &$chunk) {
    $chunk = array_pad($chunk, [2], 0);
}
print_r($chunks);
?>

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

A2

B3

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 3 for chunk size creates bigger chunks.

Padding to 0 does not add elements.

Chunks are created with size 2, then each chunk is padded to size 3 with zeros.

5fill in blank

hard

Fill all three blanks to chunk the array by 3, pad each chunk to 4 with -1, and print the result.

PHP

<?php
$values = [10, 20, 30, 40, 50, 60, 70];
$chunks = array_chunk($values, [1]);
foreach ($chunks as &$chunk) {
    $chunk = array_pad($chunk, [2], [3]);
}
print_r($chunks);
?>

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

A3

B4

C-1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 as padding value adds zeros instead of -1.

Padding to 3 does not add extra elements.

The array is split into chunks of 3 elements, then each chunk is padded to length 4 with -1.

Practice

1. What does the PHP function array_chunk do?

easy

A. Splits an array into smaller arrays of a fixed size

B. Adds elements to the end of an array to reach a certain size

C. Removes duplicate values from an array

D. Sorts an array in ascending order

Solution

1. Step 1: Understand the function purpose

   array_chunk is designed to split a large array into smaller arrays each having a fixed number of elements.

2. Step 2: Compare with other options

   Adding elements to reach a size is done by array_pad, not array_chunk. Removing duplicates or sorting are unrelated functions.

3. Final Answer:

   Splits an array into smaller arrays of a fixed size -> Option A

4. Quick Check:

   array_chunk = split array [OK]

Hint: Remember: chunk means break into pieces [OK]

Common Mistakes:

• Confusing array_chunk with array_pad
• Thinking it sorts or removes duplicates
• Assuming it modifies the original array in place

2. Which of the following is the correct syntax to pad an array $arr to size 5 with the value 0 using array_pad?

easy

A. $padded = array_pad($arr, 5);

B. $padded = array_pad(5, $arr, 0);

C. $padded = array_pad($arr, 5, 0);

D. $padded = array_pad($arr, 0, 5);

Solution

1. Step 1: Recall array_pad syntax

   The correct syntax is array_pad(array, size, value), where the first argument is the array, second is the desired size, third is the padding value.

2. Step 2: Check each option

   $padded = array_pad($arr, 5, 0); matches the correct order and arguments. Options B and C have wrong argument order. $padded = array_pad($arr, 5); misses the padding value.

3. Final Answer:

   $padded = array_pad($arr, 5, 0); -> Option C

4. Quick Check:

   array_pad(array, size, value) correct order [OK]

Hint: Remember: array_pad(array, size, value) [OK]

Common Mistakes:

• Swapping argument order
• Omitting the padding value
• Passing size as first argument

3. What is the output of the following PHP code?

$arr = [1, 2, 3, 4, 5];
$chunks = array_chunk($arr, 2);
print_r($chunks);

medium

A. [[1, 2, 3], [4, 5]]

B. [[1, 2], [3, 4], [5]]

C. [[1, 2], [3, 4], [5, null]]

D. [1, 2, 3, 4, 5]

Solution

1. Step 1: Understand array_chunk behavior

   array_chunk splits the array into smaller arrays each with 2 elements, except the last chunk which may have fewer if elements run out.

2. Step 2: Apply to given array

   Splitting [1,2,3,4,5] by 2 gives chunks: [1,2], [3,4], and [5]. No padding is added by array_chunk.

3. Final Answer:

   [[1, 2], [3, 4], [5]] -> Option B

4. Quick Check:

   array_chunk splits into groups of 2 [OK]

Hint: Last chunk may be smaller if not divisible [OK]

Common Mistakes:

• Expecting padding in array_chunk
• Confusing chunk size with number of chunks
• Assuming all chunks have equal length always

4. Identify the error in this PHP code snippet:

$arr = [1, 2];
$padded = array_pad($arr, 5);
print_r($padded);

medium

A. print_r cannot print arrays

B. array_pad cannot increase array size

C. array_pad requires the size to be smaller than original

D. Missing the padding value argument in array_pad

Solution

1. Step 1: Check array_pad function signature

   array_pad requires three arguments: the array, the new size, and the value to pad with.

2. Step 2: Identify missing argument

   The code calls array_pad with only two arguments, missing the padding value, which causes an error.

3. Final Answer:

   Missing the padding value argument in array_pad -> Option D

4. Quick Check:

   array_pad needs 3 arguments [OK]

Hint: array_pad needs array, size, and value [OK]

Common Mistakes:

• Forgetting the padding value
• Assuming array_pad works with two arguments
• Thinking print_r can't print arrays

5. You have an array $data = [10, 20, 30]. You want to split it into chunks of size 2 and ensure each chunk has exactly 2 elements by padding with 0 if needed. Which code correctly achieves this?

hard

A. $chunks = array_chunk($data, 2);
foreach ($chunks as &$chunk) {
$chunk = array_pad($chunk, 2, 0);
}
print_r($chunks);

B. $chunks = array_pad(array_chunk($data, 2), 2, 0);
print_r($chunks);

C. $chunks = array_chunk(array_pad($data, 5, 0), 2);
print_r($chunks);

D. $chunks = array_chunk($data, 2, 0);
print_r($chunks);

Solution

1. Step 1: Understand the goal

   We want chunks of size 2, each chunk exactly length 2, padding with 0 if chunk is smaller.

2. Step 2: Analyze each option

   $chunks = array_chunk($data, 2); foreach ($chunks as &$chunk) { $chunk = array_pad($chunk, 2, 0); } print_r($chunks); splits into chunks, then pads each chunk to size 2 with 0, which is correct.
   $chunks = array_pad(array_chunk($data, 2), 2, 0); print_r($chunks); tries to pad the array of chunks, which is incorrect.
   $chunks = array_chunk(array_pad($data, 5, 0), 2); print_r($chunks); pads the original array to size 5, then chunks, which may add unwanted extra elements.
   $chunks = array_chunk($data, 2, 0); print_r($chunks); passes 0 as third argument to array_chunk, which is invalid.

3. Final Answer:

   $chunks = array_chunk($data, 2); foreach ($chunks as &$chunk) { $chunk = array_pad($chunk, 2, 0); } print_r($chunks); -> Option A

4. Quick Check:

   Pad each chunk after chunking [OK]

Hint: Pad each chunk after chunking, not the whole array [OK]

Common Mistakes:

• Padding the whole array before chunking
• Passing extra arguments to array_chunk
• Trying to pad the array of chunks directly