Sort and Filter Arrays in PHP: usort, array

Sort and filter arrays in PHP with the functions built for the job — no hand-rolled loops. This tutorial takes one array of product rows and reshapes it five ways: sort() and rsort() order a flat list, asort() orders values while keeping their keys, usort() sorts rows by any column you choose, array_filter() keeps only the rows that pass a test, and array_map() transforms every row into something new. Finally, array_column() plucks a single field out of every row. These are the same arrays a CSV or JSON import hands you, so the recipes apply the moment data arrives.

Requirements to sort and filter arrays in PHP:

PHP 7.4 or newer — tested on PHP 8.5.7 from the command line. In addition, every function here is core PHP; nothing to install.

How To Sort and Filter the Arrays in PHP.

The objective is to answer real questions about a product list — cheapest to dearest, most expensive first, which cost under 100, what each line of stock is worth — each with one function call.

Step 1.

First, the data. Save this as arrays.php; each row is an associative array, exactly the shape you get, for example, from a database fetch or a parsed CSV line.

$products = [
    ['name' => 'Standing Desk',       'category' => 'Desks',       'price' => 412.50, 'stock' => 5],
    ['name' => 'Mechanical Keyboard', 'category' => 'Keyboards',   'price' => 89.00,  'stock' => 24],
    ['name' => '27-inch Monitor',     'category' => 'Monitors',    'price' => 249.00, 'stock' => 11],
    ['name' => 'Desk Lamp',           'category' => 'Lighting',    'price' => 34.99,  'stock' => 40],
    ['name' => 'Wireless Mouse',      'category' => 'Accessories', 'price' => 19.95,  'stock' => 60],
];

Step 2.

Next, sort a flat list. sort() orders values ascending and rsort() descending — both work in place and re-number the keys. When the keys carry meaning, use asort() instead: it sorts the values but keeps each value glued to its key (ksort() is its sibling that sorts by the keys themselves).

$prices = array_column($products, 'price');
sort($prices);    // 19.95, 34.99, 89, 249, 412.5
rsort($prices);   // 412.5, 249, 89, 34.99, 19.95

$stockByName = array_column($products, 'stock', 'name');
asort($stockByName);
print_r($stockByName);

Array
(
    [Standing Desk] => 5
    [27-inch Monitor] => 11
    [Mechanical Keyboard] => 24
    [Desk Lamp] => 40
    [Wireless Mouse] => 60
)

Step 3.

Then, sort rows by a column with usort(). You supply the rule as a comparator function, and the spaceship operator <=> does the three-way comparison. Swapping $a and $b flips the direction, so as written, the priciest row comes first.

usort($products, function ($a, $b) {
    return $b['price'] <=> $a['price'];
});

most expensive first:
  Standing Desk          412.50
  27-inch Monitor        249.00
  Mechanical Keyboard     89.00
  Desk Lamp               34.99
  Wireless Mouse          19.95

Step 4.

Now filter. array_filter() calls your test for every row and keeps the rows where it returns true. However, it preserves the original keys — wrap the result in array_values() if you need a clean 0,1,2… sequence afterwards.

$affordable = array_filter($products, function ($p) {
    return $p['price'] < 100;
});

under 100:
  Mechanical Keyboard
  Desk Lamp
  Wireless Mouse

Step 5.

Transform with array_map(). Instead of changing the original, it builds a new array by passing every row through your function — here, turning each product into a name plus the value of its stock on the shelf.

$stockValue = array_map(function ($p) {
    return ['name' => $p['name'], 'value' => $p['price'] * $p['stock']];
}, $products);

stock value per product:
  Standing Desk         2062.50
  27-inch Monitor       2739.00
  Mechanical Keyboard   2136.00
  Desk Lamp             1399.60
  Wireless Mouse        1197.00

Step 6.

Finally, pluck one field from every row with array_column(). One call replaces a whole foreach, and an optional third argument (used in Step 2) also sets another column as the keys.

$names = array_column($products, 'name');
echo implode(' | ', $names);

Result when you sort and filter arrays in PHP.

Once you run arrays.php from the terminal, it prints every reshaped view of the same five rows — sorted flat, sorted by column, filtered, transformed, and plucked. This is the real output from PHP 8.5.7:

sorted prices:  19.95, 34.99, 89, 249, 412.5
reversed:       412.5, 249, 89, 34.99, 19.95

most expensive first:
  Standing Desk          412.50
  27-inch Monitor        249.00
  Mechanical Keyboard     89.00

under 100:
  Mechanical Keyboard
  Desk Lamp
  Wireless Mouse

names: Standing Desk | 27-inch Monitor | Mechanical Keyboard | ...

Notes on how to sort and filter arrays in PHP:

Sorts mutate, transforms copy. sort(), rsort(), asort() and usort() change the array you pass in and return true. In contrast, array_filter(), array_map() and array_column() leave the original untouched and return a new array.
Also, arrow functions shorten every callback here: array_filter($products, fn ($p) => $p['price'] < 100).
Sorting strings that contain numbers? sort($files, SORT_NATURAL) orders img2 before img10; the default string sort does not.
To sort by two columns, compare the second when the first ties: return [$a['category'], $a['price']] <=> [$b['category'], $b['price']]; — the spaceship compares arrays element by element.
These functions pick up right where parsing leaves off — the row arrays here are exactly what you get after reading a CSV file in PHP or parsing a JSON file.

Sort and Filter Arrays in PHP