Array chunk and pad in PHP - Mini Project: Build & Apply

Array chunk and pad

📖 Scenario: You are organizing a list of guests for a dinner party. You want to split the guests into tables with a fixed number of seats. If a table has fewer guests than seats, you want to fill the empty seats with the word "Empty".

🎯 Goal: Create a PHP program that splits an array of guest names into smaller arrays (tables) of a fixed size. If a table has fewer guests than the fixed size, fill the remaining seats with "Empty".

📋 What You'll Learn

Create an array called guests with exactly these names: 'Anna', 'Ben', 'Cara', 'David', 'Eva', 'Frank', 'Grace'

Create a variable called tableSize and set it to 3

Use array_chunk with the $preserve_keys parameter set to false to split guests into chunks of size tableSize

Use array_pad to fill any chunk smaller than tableSize with the string 'Empty'

Print the final array of tables

💡 Why This Matters

🌍 Real World

Organizing guests into tables for events or dinners where each table has a fixed number of seats.

💼 Career

Helps in understanding how to manipulate arrays for grouping data and filling missing values, useful in data processing and UI display tasks.

1

Create the guests array

Create an array called guests with these exact names: 'Anna', 'Ben', 'Cara', 'David', 'Eva', 'Frank', 'Grace'.

PHP

# Create the array called guests with the given names
# Your code here

Hint

Use square brackets [] to create the array and separate names with commas.

2

Set the table size

Create a variable called tableSize and set it to 3.

PHP

<?php
$guests = ['Anna', 'Ben', 'Cara', 'David', 'Eva', 'Frank', 'Grace'];
# Create the variable tableSize and set it to 3
# Your code here

Hint

Use the = sign to assign the value 3 to $tableSize.

3

Split guests into tables and pad

Use array_chunk with the $preserve_keys parameter set to false to split $guests into chunks of size $tableSize. Then, use a foreach loop with variables $index and $table to iterate over the chunks. Inside the loop, use array_pad to fill any chunk smaller than $tableSize with the string 'Empty'. Store the padded tables in a new array called paddedTables.

PHP

<?php
$guests = ['Anna', 'Ben', 'Cara', 'David', 'Eva', 'Frank', 'Grace'];
$tableSize = 3;
# Split guests into chunks of size tableSize without preserving keys
$tables = array_chunk($guests, $tableSize, false);
# Create an empty array paddedTables
$paddedTables = [];
# Use foreach with index and table to pad each chunk to tableSize with 'Empty'
# Your code here

Hint

Use array_chunk to split the array, then loop over each chunk and use array_pad to add 'Empty' if needed.

4

Print the padded tables

Print the array paddedTables using print_r to display the final tables with padding.

PHP

 $table) {
    $paddedTables[$index] = array_pad($table, $tableSize, 'Empty');
}
# Print the paddedTables array
# Your code here

Hint

Use print_r($paddedTables); to show the array structure.

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