Array slice and splice in PHP

Introduction

Array slice and splice help you take parts of an array or change it by adding or removing items.

You want to get a smaller part of a big list without changing the original.

You need to remove some items from a list and keep the rest.

You want to add new items inside a list at a specific place.

You want to replace some items in a list with new ones.

You want to copy a list or part of it to use somewhere else.

Syntax

PHP

<?php
// Array slice syntax
$sliced_array = array_slice(array $array, int $offset, ?int $length = null, bool $preserve_keys = false);

// Array splice syntax
$removed_elements = array_splice(array &$array, int $offset, ?int $length = null, mixed $replacement = []);
?>

array_slice returns a new array and does not change the original array.

array_splice changes the original array by removing and optionally adding elements.

Examples

This takes 2 items starting from index 1 ('banana' and 'cherry'). The original array stays the same.

PHP

<?php
// Example 1: Slice part of an array
$fruits = ['apple', 'banana', 'cherry', 'date'];
$sliced = array_slice($fruits, 1, 2);
print_r($sliced);

This takes all items from index 2 to the end (30, 40).

PHP

<?php
// Example 2: Slice with offset only
$numbers = [10, 20, 30, 40];
$sliced = array_slice($numbers, 2);
print_r($sliced);

This removes 2 items starting at index 1 ('green', 'blue') from the original array.

PHP

<?php
// Example 3: Splice to remove elements
$colors = ['red', 'green', 'blue', 'yellow'];
$removed = array_splice($colors, 1, 2);
print_r($colors);
print_r($removed);

This replaces 'b' and 'c' with 'x' and 'y' in the original array.

PHP

<?php
// Example 4: Splice to replace elements
$letters = ['a', 'b', 'c', 'd'];
array_splice($letters, 1, 2, ['x', 'y']);
print_r($letters);

Sample Program

This program shows how array_slice returns a new part without changing the original array. Then it shows how array_splice removes some elements and adds new ones, changing the original array.

PHP

<?php
// Create an array
$animals = ['cat', 'dog', 'bird', 'fish', 'horse'];

// Print original array
echo "Original array:\n";
print_r($animals);

// Use array_slice to get a part without changing original
$sliced_animals = array_slice($animals, 1, 3);
echo "\nSliced array (index 1 to 3):\n";
print_r($sliced_animals);

echo "\nArray after slice (unchanged):\n";
print_r($animals);

// Use array_splice to remove and replace elements
$removed_animals = array_splice($animals, 2, 2, ['lion', 'tiger']);
echo "\nRemoved elements by splice:\n";
print_r($removed_animals);

echo "\nArray after splice (changed):\n";
print_r($animals);
?>

Important Notes

Time complexity: array_slice is O(n) where n is the length of the slice; array_splice is O(m) where m is the number of elements removed or added.

Space complexity: array_slice creates a new array, so it uses extra space; array_splice modifies in place, so uses less extra space.

Common mistake: Expecting array_splice to return the changed array. It returns the removed elements instead.

Use array_slice when you want a copy of part of the array without changing the original. Use array_splice when you want to change the original array by removing or adding items.

Summary

array_slice returns a new array with selected elements and does not change the original.

array_splice removes and/or adds elements in the original array and returns the removed elements.

Use slice to copy parts, splice to change the array.