PHP Multipart array to Guzzle Client or other ...

multipart.php

<?php

/**
 * Turns associative arrays into multipart [['name' => 'key[0][deep]', 'contents' => 'value']]
 */
function array_multipart(array $data = [])
{
    $dots = array_dot($data);
    $multipart = [];

    foreach ($dots as $key => $content) {
        $multipart[] = [
            'name' => bracket_from_dots($key),
            'contents' => $content
        ];
    }

    return $multipart;
}

/**
 * Flatten a multi-dimensional associative array with dots.
 *
 * @param  iterable  $array
 * @param  string  $prepend
 * @return array
 */
function array_dot($array, $prepend = '')
{
    $results = [];

    foreach ($array as $key => $value) {
        if (is_array($value) && ! empty($value)) {
            $results = array_merge($results, array_dot($value, $prepend.$key.'.'));
        } else {
            $results[$prepend.$key] = $value;
        }
    }

    return $results;
}

function bracket_from_dots($key)
{
    $segments = explode('.', $key);
    $result = array_shift($segments);

    foreach ($segments as $name) {
        $result .= "[{$name}]";
    }

    return $result;
}