The array_slice() function in PHP is used to extract a portion of an array based on specified offsets and lengths. It returns a new array containing the extracted elements without modifying the original array. This function is particularly useful for paginating results or working with subsets of data.

Syntax:

array_slice(array $array, int $offset, int|null $length = null, bool $preserve_keys = false): array

Parameters:

• $array: The input array from which to extract elements.
• $offset: The starting index from which to begin extraction. A negative offset can be used to count from the end of the array.
• $length: (Optional) The number of elements to extract. If not provided, it will extract all elements from the offset to the end of the array. If the length is negative, it will stop that many elements from the end of the array.
• $preserve_keys: (Optional) A boolean that determines whether to preserve the original keys of the array. If set to true, the keys will be preserved; if false (the default), the keys will be re-indexed starting from 0.

Return Value:

• Returns a new array containing the extracted elements.

Example 1: Basic Usage

In this example, we demonstrate how to use array_slice() to extract a portion of an array.

<?php
$array = [1, 2, 3, 4, 5];
$slicedArray = array_slice($array, 2);

print_r($slicedArray);
?>

Output:

Array
(
    [0] => 3
    [1] => 4
    [2] => 5
)

In this case, the extraction starts from index 2, and the result is an array containing elements from index 2 to the end.

Example 2: Specifying Length

You can specify a length to control how many elements to extract.

<?php
$array = [1, 2, 3, 4, 5];
$slicedArray = array_slice($array, 1, 3);

print_r($slicedArray);
?>

Output:

Array
(
    [0] => 2
    [1] => 3
    [2] => 4
)

Here, starting from index 1, three elements are extracted, resulting in an array containing 2, 3, and 4.

Example 3: Negative Offset

Using a negative offset allows you to extract elements starting from the end of the array.

<?php
$array = [1, 2, 3, 4, 5];
$slicedArray = array_slice($array, -2);

print_r($slicedArray);
?>

Output:

Array
(
    [0] => 4
    [1] => 5
)

In this case, the extraction starts from the second-to-last element and goes to the end of the array.

Example 4: Preserving Keys

You can choose to preserve the original keys when extracting elements.

<?php
$array = ["a" => "apple", "b" => "banana", "c" => "cherry"];
$slicedArray = array_slice($array, 1, 2, true);

print_r($slicedArray);
?>

Output:

Array
(
    [b] => banana
    [c] => cherry
)

Here, starting from index 1, two elements are extracted, and the original keys b and c are preserved.

Example 5: Negative Length

You can also use a negative length to stop the extraction a certain number of elements from the end of the array.

<?php
$array = [1, 2, 3, 4, 5];
$slicedArray = array_slice($array, 0, -1);

print_r($slicedArray);
?>

Output:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
)

In this case, the function extracts elements from the start up to (but not including) the last element.

Practical Usage:

• array_slice() is useful for:
  • Implementing pagination by extracting a subset of elements for display.
  • Working with arrays where only a portion of the data is needed.
  • Creating copies of specific portions of an array for processing without altering the original data.

Summary:

• array_slice($array, $offset, $length, $preserve_keys) extracts a portion of an array based on the specified offset and length.
• It returns a new array containing the extracted elements while keeping the original array intact.
• This function is versatile and valuable for various array manipulation tasks in PHP, especially when dealing with larger datasets.