Four Ways to Reverse an Array in PHP

In PHP, arrays are a common data type that can store multiple values, and reversing an array is a frequent requirement.

Method 1: array_reverse() function

PHP provides the built‑in array_reverse() function which returns a new array with the elements in reverse order.

<code>$arr = array(1, 2, 3, 4, 5);
$reversedArr = array_reverse($arr);
print_r($reversedArr);
</code>

The output is:

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

The function can optionally preserve keys; the second parameter defaults to false . Setting it to true keeps the original keys.

<code>$arr = array("one" => 1, "two" => 2, "three" => 3, "four" => 4, "five" => 5);
$reversedArr = array_reverse($arr, true);
print_r($reversedArr);
</code>

The output is:

<code>Array
(
    [five] => 5
    [four] => 4
    [three] => 3
    [two] => 2
    [one] => 1
)
</code>

Method 2: for loop

A manual for loop can reverse an array by swapping elements from both ends using two pointers.

<code>$arr = array(1, 2, 3, 4, 5);
$len = count($arr);
for ($i = 0; $i < $len / 2; $i++) {
    $temp = $arr[$i];
    $arr[$i] = $arr[$len - $i - 1];
    $arr[$len - $i - 1] = $temp;
}
print_r($arr);
</code>

The output is:

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

Method 3: Using array_reduce() with reversed keys

The array_reduce() function can also be employed to reverse an array by iterating over its keys.

<code>$arr = array(1, 2, 3, 4, 5);
$reversedArr = array_reduce(array_keys($arr), function ($acc, $key) use ($arr) {
    $acc[$key] = $arr[count($arr) - 1 - $key];
    return $acc;
}, []);
print_r($reversedArr);
</code>

The output is:

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

This approach uses array_keys() to obtain indices and an accumulator $acc (initially an empty array) to build the reversed array. Although more complex, array_reduce() is useful for other array transformations.

Method 4: Using array_multisort() and array_column()

The final method leverages PHP's handling of multidimensional arrays. It separates odd and even indexed elements, reverses each with array_multisort() , and then recombines them using array_column() .

<code>$arr = array(1, 2, 3, 4, 5);
$n = count($arr);
for ($i = 0; $i < $n; $i++) {
    if ($i % 2 == 0) {
        $even[] = $arr[$i];
    } else {
        $odd[] = $arr[$i];
    }
}
array_multisort(array_reverse($odd), SORT_NUMERIC, array_reverse($even), SORT_NUMERIC);
$reversedArr = array_column(array($even, $odd), 0);
print_r($reversedArr);
</code>

The output is:

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

Here, the odd and even elements are stored in $odd and $even arrays, respectively; array_multisort() reverses them, and array_column() flattens the result back to a single array.

In summary, the article covers four different techniques for reversing a PHP array: the simple array_reverse() function, a manual for loop, the more versatile array_reduce() method, and a multidimensional‑array approach using array_multisort() and array_column() . The built‑in function is the most straightforward, while the other methods illustrate alternative strategies and deeper PHP capabilities.