Array Functions in PHP: A Practical Reference

PHP ships with well over 80 array functions. Most day-to-day work only needs a handful of them used well.

Transform every element: array_map

$prices = [10, 20, 30];
$withTax = array_map(fn($p) => $p * 1.18, $prices);
// [11.8, 23.6, 35.4]

array_map always returns an array the same length as the input — use it when you're changing values, not removing them.

Keep only what matches: array_filter

$ages = [22, 34, 19, 41];
$adults = array_filter($ages, fn($a) => $a >= 21);
// [0 => 22, 1 => 34, 3 => 41]  — note: keys are preserved

That preserved-keys behavior surprises people — pipe the result through array_values() if you need a clean re-indexed array:

$adults = array_values(array_filter($ages, fn($a) => $a >= 21));

Collapse to one value: array_reduce

$cart = [10, 20, 30];
$total = array_reduce($cart, fn($carry, $item) => $carry + $item, 0);
// 60

The third argument (0 here) is the initial value — always pass it explicitly, since relying on the default null produces confusing errors the moment your callback does arithmetic.

Pluck a column from an array of arrays: array_column

This one function replaces a foreach loop most people write from scratch:

$users = [
    ['id' => 1, 'name' => 'Ana'],
    ['id' => 2, 'name' => 'Ravi'],
];
 
array_column($users, 'name');          // ['Ana', 'Ravi']
array_column($users, 'name', 'id');    // [1 => 'Ana', 2 => 'Ravi']

Combining arrays: array_merge vs. the + operator

$a = ['x' => 1, 0 => 'a'];
$b = ['x' => 2, 0 => 'b'];
 
array_merge($a, $b); // ['x' => 2, 0 => 'a', 1 => 'b'] — numeric keys renumbered, string keys overwritten
$a + $b;              // ['x' => 1, 0 => 'a']          — left array wins on any key conflict

This is the single most common source of "why did my array merge wrong" bugs in PHP — array_merge renumbers integer keys but + never overwrites an existing key from the left-hand array. Pick based on whether numeric-key collisions should be renumbered or preserved.