How to fast flatten array in php.

flatten-array.php

<?php

# Flatten array and modify it's value
# [[1, 2, 3, 4, [3, 4]] => [1, 2, 3, 4, 3, 4]
# php ./script.php to test

$total = 30000;
$mockData = [];

for($i = 1; $i < $total; $i++) {
    $mockData[] = ['id' => $i, 'name' => 'sample' . $i];
}

$modifiers = [
    function ($key, $value) { return $value; },
    function ($key, $value) { if (1 === $value && 'id' === $key) { return 'changed'; } return $value; },
];

function print_result($title, \DateTime $time, $parameters, $sym) {
    $end = $time->diff(new \DateTime());

    echo \vsprintf('%s Time: %s:%s:%s:%s Size: %smb %s', [
        $title,
        $end->h, $end->i, $end->s, $end->f,
        \strlen(\serialize($parameters)) * 0.000001,
        $sym
    ]) . PHP_EOL;
}

## Method 1
$start = new \DateTime();
$data = new \RecursiveIteratorIterator(new \RecursiveArrayIterator($mockData));
$parameters = [];

$data->rewind();
while ($data->valid()) {

    $key = $data->key();
    $value = $data->current();

    \array_map(function ($modifier) use (&$value, $key) {
        $value = \call_user_func($modifier, $key, $value);
    }, $modifiers);

    $parameters[] = $value;

    $data->next();
}

print_result('#1', $start, $parameters, '🏎️');

# Method 2
$start = new \DateTime();
$parameters = \array_reduce($mockData, function (array $flattenedValues, array $valueSet) use ($modifiers) {
    \array_map(function ($modifier) use (&$valueSet) {
        \array_walk($valueSet, function (&$value, $key) use ($modifier) {
            $value = \call_user_func($modifier, $key, $value);
        });
    }, $modifiers);

    return \array_merge($flattenedValues, array_values($valueSet));
}, []);

print_result('#2', $start, $parameters, '🐢');

# Method 2x -- without modifier
$start = new \DateTime();
$parameters = \array_reduce($mockData, function (array $flattenedValues, array $valueSet) {
    return \array_merge($flattenedValues, array_values($valueSet));
}, []);

print_result('#2x', $start, $parameters, '🐢');