PHP Manual
Sequence
Reduces the sequence to a single value using a callback function

Ds\Sequence::reduce

(PECL ds >= 1.0.0)

Ds\Sequence::reduce — Reduces the sequence to a single value using a callback function

Description

abstract public Ds\Sequence::reduce ( callable $callback [, mixed $initial ] ) : mixed

Reduces the sequence to a single value using a callback function.

Parameters

callback

callback ( mixed $carry , mixed $value ) : mixed

carry: The return value of the previous callback, or initial if it's the first iteration.
value: The value of the current iteration.

initial

The initial value of the carry value. Can be NULL.

Return Values

The return value of the final callback.

Examples

Example #1 Ds\Sequence::reduce() with initial value example

<?php$sequence = new \Ds\Vector([1, 2, 3]);$callback = function($carry, $value) { return $carry * $value;};var_dump($sequence->reduce($callback, 5));// Iterations://// $carry = $initial = 5//// $carry = $carry * 1 = 5// $carry = $carry * 2 = 10// $carry = $carry * 3 = 30?>

The above example will output something similar to:

int(30)

Example #2 Ds\Sequence::reduce() without an initial value example

<?php$sequence = new \Ds\Vector([1, 2, 3]);var_dump($sequence->reduce(function($carry, $value) { return $carry + $value + 5;}));// Iterations://// $carry = $initial = null//// $carry = $carry + 1 + 5 = 6// $carry = $carry + 2 + 5 = 13// $carry = $carry + 3 + 5 = 21?>