Mastering PHP’s array_reverse(): Reverse Arrays with Ease

1. What is array_reverse()?

array_reverse()

is a PHP array function that reverses the order of elements in an array, works with indexed and associative arrays, and returns a new array without altering the original keys.

2. Syntax and parameters

Basic syntax:

array array_reverse(array $array [, bool $preserve_keys = FALSE]);

Parameters: $array: required, the array to reverse. $preserve_keys: optional, whether to keep original keys; default FALSE; if TRUE, keys are preserved.

3. Usage examples

Examples:

① Indexed array reversal:

$numbers = array(1, 2, 3, 4, 5);
$rev_numbers = array_reverse($numbers);
print_r($rev_numbers); // Array ( [0] => 5 [1] => 4 [2] => 3 [3] => 2 [4] => 1 )

② Associative array reversal:

$infos = array('name' => 'Tom', 'age' => 20, 'sex' => 'male');
$rev_infos = array_reverse($infos);
print_r($rev_infos); // Array ( [sex] => male [age] => 20 [name] => Tom )

③ Preserve keys:

$fruits = array('a' => 'apple', 'b' => 'banana', 'c' => 'cherry');
$rev_fruits = array_reverse($fruits, true);
print_r($rev_fruits); // Array ( [c] => cherry [b] => banana [a] => apple )

4. Return value

The function returns a new array with elements in reverse order. If the input array is empty, an empty array is returned. When $preserve_keys is TRUE, the returned array keeps the original keys.

5. Important notes

array_reverse()

works only on arrays, not other data types.

If $preserve_keys is TRUE, original integer keys become strings in the result.

An empty input array yields an empty result.

Conclusion

array_reverse()

is a practical PHP function for efficiently reversing array elements while optionally preserving keys, helping to write cleaner and more concise code.