PHP has one of the richest built-in array function libraries of any language — over 80 functions. Some of the most commonly used:
Transforming:
array_map(fn ($x) => $x * 2, $arr); // apply a function to every element
array_filter($arr, fn ($x) => $x > 10); // keep elements matching a condition
array_reduce($arr, fn ($c, $x) => $c + $x, 0); // fold to a single value
Sorting:
sort($arr); // sort values ascending, reindexes keys
rsort($arr); // descending
asort($arr); // sort by value, preserve keys (good for assoc arrays)
ksort($arr); // sort by key
usort($arr, fn ($a, $b) => $a['price'] <=> $b['price']); // custom comparator
Searching & checking:
in_array('red', $colors); // true/false
array_search('red', $colors); // returns the key, or false
array_key_exists('name', $arr);
Combining & slicing:
array_merge($a, $b); // combine arrays
array_slice($arr, 0, 3); // first 3 elements
array_unique($arr); // remove duplicate values
array_keys($arr); array_values($arr);
implode(', ', $arr); // array to string
explode(',', $string); // string to array
Most of these functions do not mutate the original array — they return a new one — which fits well with predictable, functional-style code.