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PHP Tutorial · Functions and Arrays · Lesson 19 of 38

PHP Array Functions

Sort, search, filter, map and reduce arrays.

Sorting

Function Sorts by Keeps keys?
sort / rsort value asc / desc no
asort / arsort value asc / desc yes
ksort / krsort key asc / desc yes
usort your compare function no

Sorting functions change the array in place and return true.

Example 1Try it yourself
<?php
$scores = ["ada" => 92, "lin" => 78, "sam" => 85];
arsort($scores);
print_r($scores);
$people = [["name" => "Zoe", "age" => 30], ["name" => "Al", "age" => 25]];
usort($people, fn($a, $b) => $a["age"] <=> $b["age"]);
echo implode(", ", array_column($people, "name")), "\n";

Output

Array
(
    [ada] => 92
    [sam] => 85
    [lin] => 78
)
Al, Zoe

Searching

Example 2Try it yourself
<?php
$langs = ["php", "go", "rust"];
var_dump(in_array("go", $langs));
var_dump(array_search("rust", $langs));
var_dump(array_search("java", $langs));

Output

bool(true)
int(2)
bool(false)

map, filter, reduce

Example 3Try it yourself
<?php
$nums = [1, 2, 3, 4, 5, 6];
$squares = array_map(fn($n) => $n * $n, $nums);
$evens = array_filter($nums, fn($n) => $n % 2 === 0);
$sum = array_reduce($nums, fn($carry, $n) => $carry + $n, 0);
echo implode(" ", $squares), "\n";
print_r($evens);           // keys are preserved!
print_r(array_values($evens));
echo $sum, "\n";

Output

1 4 9 16 25 36
Array
(
    [1] => 2
    [3] => 4
    [5] => 6
)
Array
(
    [0] => 2
    [1] => 4
    [2] => 6
)
21

Other everyday helpers

array_keys, array_values, array_merge, array_slice, array_unique, array_column, array_combine, range, implode and explode:

Example 4Try it yourself
<?php
$csv = "red,green,blue,green";
$colors = explode(",", $csv);
print_r(array_unique($colors));
echo implode(" | ", array_slice($colors, 1, 2)), "\n";
print_r(array_merge(["a" => 1], ["b" => 2, "a" => 3]));
echo implode(",", range(1, 10, 3)), "\n";

Output

Array
(
    [0] => red
    [1] => green
    [2] => blue
)
green | blue
Array
(
    [a] => 3
    [b] => 2
)
1,4,7,10

Test yourself

Which function sorts an associative array by value and keeps the keys?

  1. sort()
  2. asort()
  3. ksort()
  4. usort()
Show answer

Answer: asort()

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