Simple canonicalization of a JSON string.

JsonCanonicalizer.php

<?php

/**
 * Simple canonicalization of a JSON string.
 *
 * - removes formatting
 * - sorts object properties
 */
class JsonCanonicalizer
{
    /**
     * @param string $json
     *
     * @return string
     *
     * @throws \JsonException
     */
    public static function canonicalize(string $json) : string
    {
        $data = json_decode($json, false, 512, JSON_THROW_ON_ERROR);
        $data = self::doCanonicalize($data);

        return json_encode($data, JSON_THROW_ON_ERROR);
    }

    /**
     * @param mixed $data
     *
     * @return mixed
     */
    private static function doCanonicalize($data)
    {
        if (is_object($data)) {
            $data = (array) $data;
            ksort($data);

            foreach ($data as $key => $value) {
                $data[$key] = self::doCanonicalize($value);
            }

            return (object) $data;
        }

        if (is_array($data)) {
            foreach ($data as $key => $value) {
                $data[$key] = self::doCanonicalize($value);
            }
        }

        return $data;
    }
}