(PECL ds >= 1.0.0)
Ds\Map::reduce — Reduces the map to a single value using a callback function
public Ds\Map::reduce ( callable $callback [, mixed $initial ] ) : mixed
Reduces the map to a single value using a callback function.
callback
callback ( mixed $carry , mixed $key , mixed $value ) : mixed
carry
The return value of the previous callback, or initial if it's the first iteration.
key
The key of the current iteration.
value
The value of the current iteration.
initial
The initial value of the carry value. Can be null.
The return value of the final callback.
Example #1 Ds\Map::reduce() with initial value example
<?php
$map = new \Ds\Map(["a" => 1, "b" => 2, "c" => 3]);
$callback = function($carry, $key, $value) {
return $carry * $value;
};
var_dump($map->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\Map::reduce() without an initial value example
<?php
$map = new \Ds\Map(["a" => 1, "b" => 2, "c" => 3]);
var_dump($map->reduce(function($carry, $key, $value) {
return $carry + $value + 5;
}));
// Iterations:
//
// $carry = $initial = null
//
// $carry = $carry + 1 + 5 = 6
// $carry = $carry + 2 + 5 = 13
// $carry = $carry + 3 + 5 = 21
?> The above example will output something similar to:
int(21)
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https://www.php.net/manual/en/ds-map.reduce.php