Using PHP's array_chunk() Function to Split Arrays

In PHP development, handling arrays is a common task, and sometimes you need to split a large array into several smaller arrays of a specified size, which is where the array_chunk() function comes into play. This article introduces the usage of array_chunk() and provides several code examples.

The syntax of the function is:

array array_chunk ( array $array , int $size [, bool $preserve_keys = false ] )

The function accepts three parameters: $array – the input array to be split. $size – the size of each resulting chunk. $preserve_keys – a boolean that determines whether the original keys are preserved in the chunks (default is false).

Below is a simple example that splits an array into chunks of size 3:

<?php
$array = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j');
$chunks = array_chunk($array, 3);
print_r($chunks);
?>

The output shows the original array divided into four sub‑arrays, each containing three elements except the last one, which contains a single element:

Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
            [2] => c
        )

    [1] => Array
        (
            [0] => d
            [1] => e
            [2] => f
        )

    [2] => Array
        (
            [0] => g
            [1] => h
            [2] => i
        )

    [3] => Array
        (
            [0] => j
        )

)

By default the keys are re‑indexed, but you can preserve the original keys by passing true as the third argument. The following example demonstrates this:

<?php
$array = array('a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5, 'f' => 6);
$chunks = array_chunk($array, 2, true);
print_r($chunks);
?>

The result is three sub‑arrays that retain the original associative keys:

Array
(
    [0] => Array
        (
            [a] => 1
            [b] => 2
        )

    [1] => Array
        (
            [c] => 3
            [d] => 4
        )

    [2] => Array
        (
            [e] => 5
            [f] => 6
        )

)

In summary, the array_chunk() function is a practical tool for splitting large arrays into smaller pieces and optionally preserving the original keys, which can simplify many backend data‑processing scenarios in PHP.

php8, here I come

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