Array slice and splice in PHP - Step-by-Step Execution

Concept Flow - Array slice and splice

Start with original array

↓

Choose slice or splice

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Slice: Extract part

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Return new array

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End

You start with an array, then choose slice to get a part without changing the original, or splice to remove/insert parts and change the original.

Execution Sample

PHP

<?php
$arr = [10, 20, 30, 40, 50];
$slice = array_slice($arr, 1, 3);
array_splice($arr, 2, 2, [99, 100]);
print_r($slice);
print_r($arr);
?>

This code slices a part of the array and then splices (removes and inserts) elements, showing both results.

Execution Table

Step	Action	Array Before	Parameters	Array After	Output
1	Define original array	N/A	N/A	[10, 20, 30, 40, 50]	N/A
2	Slice from index 1, length 3	[10, 20, 30, 40, 50]	start=1, length=3	[10, 20, 30, 40, 50]	[20, 30, 40]
3	Splice at index 2, remove 2, insert [99, 100]	[10, 20, 30, 40, 50]	start=2, length=2, insert=[99,100]	[10, 20, 99, 100, 50]	N/A
4	Print slice array	[10, 20, 99, 100, 50]	N/A	[10, 20, 99, 100, 50]	[20, 30, 40]
5	Print modified original array	[10, 20, 99, 100, 50]	N/A	[10, 20, 99, 100, 50]	[10, 20, 99, 100, 50]

💡 All steps completed, slice returned new array, splice modified original array.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
$arr	N/A	[10, 20, 30, 40, 50]	[10, 20, 99, 100, 50]	[10, 20, 99, 100, 50]
$slice	N/A	[20, 30, 40]	[20, 30, 40]	[20, 30, 40]

Key Moments - 3 Insights

Why does array_slice not change the original array?

Because array_slice returns a new array with the selected elements, leaving the original array unchanged, as shown in step 2 of the execution_table.

How does array_splice modify the original array?

array_splice removes elements starting at the given index and inserts new elements if provided, changing the original array directly, as seen in step 3 where $arr changes.

What happens if the length parameter in array_slice is longer than the remaining elements?

array_slice returns all elements from the start index to the end without error, just fewer elements than requested, similar to how step 2 extracts 3 elements starting at index 1.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is the value of $slice?

A [30, 40, 50]

B [10, 20, 30]

C [20, 30, 40]

D [99, 100, 50]

💡 Hint

Check the Output column at step 2 in execution_table.

At which step does the original array $arr get modified?

A Step 3

B Step 4

C Step 2

D Step 5

💡 Hint

Look at the Array After column for $arr changes in execution_table.

If we change array_splice to remove 1 element instead of 2, how would $arr look after step 3?

A [10, 20, 99, 100, 50]

B [10, 20, 99, 100, 40, 50]

C [10, 20, 30, 40, 50]

D [10, 20, 99, 40, 50]

💡 Hint

Removing fewer elements means more original elements stay; check how splice works in execution_table step 3.

Concept Snapshot

array_slice(array, start, length) returns a new array slice without changing original.
array_splice(array, start, length, replacement) removes and inserts elements, modifying original.
Slice keeps original intact; splice changes it.
Start index is zero-based.
Length is optional in slice; in splice it controls removal count.
Splice can insert elements by passing replacement array.

Full Transcript

This visual trace shows how PHP's array_slice and array_splice work. We start with an original array. array_slice extracts a part from it without changing the original array, returning a new array. array_splice removes elements from the original array starting at a given index and can insert new elements, modifying the original array directly. The execution table tracks each step, showing the array before and after each operation, parameters used, and outputs. The variable tracker follows the values of $arr and $slice through the steps. Key moments clarify common confusions like why slice doesn't change the original and how splice modifies it. The quiz tests understanding by asking about values at specific steps and effects of parameter changes. The snapshot summarizes the main points for quick review.