Array chunk and pad in PHP - Step-by-Step Execution

Concept Flow - Array chunk and pad

Start with original array

↓

Split array into chunks of size N

↓

Check last chunk size

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Done

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Done

We start with an array, split it into smaller arrays (chunks) of a fixed size, then if the last chunk is smaller, we add extra values to fill it.

Execution Sample

PHP

<?php
$array = [1, 2, 3, 4, 5];
$chunks = array_chunk($array, 2);
$chunks[count($chunks) - 1] = array_pad($chunks[count($chunks) - 1], 2, 0);
print_r($chunks);
?>

This code splits an array into chunks of 2 elements, then pads the last chunk with zeros if it has less than 2 elements.

Execution Table

Step	Action	Array State	Chunk Created	Last Chunk Size	Padding Applied
1	Start with array	[1, 2, 3, 4, 5]	-	-	-
2	Chunk array into size 2	[1, 2, 3, 4, 5]	[[1,2],[3,4],[5]]	3rd chunk size = 1	-
3	Check last chunk size	[[1,2],[3,4],[5]]	-	1 < 2 (chunk size)	No
4	Pad last chunk with 0	[[1,2],[3,4],[5]]	-	1 < 2	Last chunk padded to [5,0]
5	Final chunks	[[1,2],[3,4],[5,0]]	-	-	-

💡 Last chunk size reached desired chunk size after padding, process complete.

Variable Tracker

Variable	Start	After Step 2	After Step 4	Final
$array	[1,2,3,4,5]	[1,2,3,4,5]	[1,2,3,4,5]	[1,2,3,4,5]
$chunks	N/A	[[1,2],[3,4],[5]]	[[1,2],[3,4],[5,0]]	[[1,2],[3,4],[5,0]]
Last chunk size	N/A	1	2	2

Key Moments - 2 Insights

Why do we need to pad only the last chunk?

Because only the last chunk can be smaller than the chunk size after splitting. Earlier chunks are always full size (see execution_table step 2 and 3).

What happens if the original array size is exactly divisible by chunk size?

No padding is needed because all chunks are full size. The check in step 3 will find last chunk size equals chunk size, so no padding is applied.

Visual Quiz - 3 Questions

Look at the execution table, what is the size of the last chunk after step 2?

A 1

B 2

C 3

D 0

💡 Hint

Check the 'Last Chunk Size' column at step 2 in the execution_table.

At which step is padding applied to the last chunk?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look for 'Padding Applied' column in execution_table where padding is mentioned.

If the original array was [1,2,3,4], how many chunks would be created with chunk size 2?

A 3

B 1

C 2

D 4

💡 Hint

Divide array length 4 by chunk size 2 and check execution_table logic.

Concept Snapshot

array_chunk(array, size) splits array into chunks of given size.
array_pad(array, size, value) adds value to array until it reaches size.
Use array_chunk first, then pad only the last chunk if smaller.
Padding fills missing elements to keep chunk size consistent.
No padding needed if last chunk is already full size.

Full Transcript

This example shows how to split an array into smaller parts called chunks using array_chunk. Each chunk has a fixed size. If the last chunk is smaller, we add extra values using array_pad to fill it. We start with the original array, split it, check the last chunk size, and pad if needed. This ensures all chunks have the same size. Padding is only done on the last chunk because earlier chunks are always full. If the array size divides evenly by chunk size, no padding is needed. This process helps when you want equal-sized groups from an array.