src/Composer/Json/JsonFile.php
public static function encode($data, $options = 448)
    {
        if (PHP_VERSION_ID >= 50400) {
            $json = json_encode($data, $options);
            if (false === $json) {
                self::throwEncodeError(json_last_error());
            }

            //  compact brackets to follow recent php versions
            if (PHP_VERSION_ID < 50428 || (PHP_VERSION_ID >= 50500 && PHP_VERSION_ID < 50512) || (defined('JSON_C_VERSION') && version_compare(phpversion('json'), '1.3.6', '<'))) {
                $json = preg_replace('/\[\s+\]/', '[]', $json);
                $json = preg_replace('/\{\s+\}/', '{}', $json);
            }

            return $json;
        }

        $json = json_encode($data);
        if (false === $json) {
            self::throwEncodeError(json_last_error());
        }

        $prettyPrint = (bool) ($options & self::JSON_PRETTY_PRINT);
        $unescapeUnicode = (bool) ($options & self::JSON_UNESCAPED_UNICODE);
        $unescapeSlashes = (bool) ($options & self::JSON_UNESCAPED_SLASHES);

        if (!$prettyPrint && !$unescapeUnicode && !$unescapeSlashes) {
            return $json;
        }

        return JsonFormatter::format($json, $unescapeUnicode, $unescapeSlashes);
    }
public static function encode($data, $options = 448)
    {
        if (PHP_VERSION_ID >= 50400) {
            $json = json_encode($data, $options);
            if (false === $json) {
                self::throwEncodeError(json_last_error());
            }

            //  compact brackets to follow recent php versions
            if (PHP_VERSION_ID < 50428 || (PHP_VERSION_ID >= 50500 && PHP_VERSION_ID < 50512) || (defined('JSON_C_VERSION') && version_compare(phpversion('json'), '1.3.6', '<'))) {
                $json = preg_replace('/\[\s+\]/', '[]', $json);
                $json = preg_replace('/\{\s+\}/', '{}', $json);
            }

            return $json;
        }

        $json = json_encode($data);
        if (false === $json) {
            self::throwEncodeError(json_last_error());
        }

        $prettyPrint = (bool) ($options & self::JSON_PRETTY_PRINT);
        $unescapeUnicode = (bool) ($options & self::JSON_UNESCAPED_UNICODE);
        $unescapeSlashes = (bool) ($options & self::JSON_UNESCAPED_SLASHES);

        if (!$prettyPrint && !$unescapeUnicode && !$unescapeSlashes) {
            return $json;
        }

        return JsonFormatter::format($json, $unescapeUnicode, $unescapeSlashes);
    }
Encodes an array into (optionally pretty-printed) JSON

@param  mixed  $data    Data to encode into a formatted JSON string
@param  int    $options json_encode options (defaults to JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE)
@return string Encoded json