Simple fast bidirectional mapping between scalars and strings

scalar_serializer.php

<?php

class ScalarSerializer {
    /**
     * @param string $s
     * @return string|int|float|bool|null
     */
    static function unserialize($s) {
        $t = (string)substr($s, 0, 1);
        $v = (string)substr($s, 1);
        switch ($t) {
        case 'b':
            return (bool) $v;
        case 'i':
            return (int) $v;
        case 'f':
            return (float) $v;
        case ':':
            return $v;
        case '~':
            return null;
        default:
            throw new \Exception('Unhandled type tag: ' . $t);
        }
    }

    /**
     * @param string|int|float|bool|null $x
     * @return string
     */
    static function serialize($x) {
        if (is_string($x)) {
            return ':' . $x;
        } else if (is_int($x)) {
            return 'i' . $x;
        } else if (is_null($x)) {
            return '~';
        } else if (is_bool($x)) {
            return 'b' . ($x ? '1' : '0');
        } else if (is_float($x)) {
            if (is_finite($x)) {
                list($l, $r) = explode('.', number_format(abs($x), 400, '.', ''), 2);
                $l = $l ?: '0';
                $r = $r ?: '0';
                $n = $x < 0 ? '-' : '';
                return "f$n$l.$r";
            } else {
                throw new \Exception('INF, -INF and NAN are not supported');
            }
        } else {
            throw new \Exception('Unhandled type: ' . gettype($x));
        }
    }

    /**
     * @return void
     */
    static function test() {
        static $values = array(
            'hello',
            '',
            "\x00",
            null,
            true,
            false,
            -1.0/3.0,
            0,
            2,
            -9,
            PHP_INT_MAX,
        );

        foreach ($values as $v1) {
            $s  = ScalarSerializer::serialize($v1);
            $v2 = ScalarSerializer::unserialize($s);
            if ($v1 !== $v2) {
                $v1 = var_export($v1, true);
                $v2 = var_export($v2, true);
                throw new \Exception("Failed to serialize $v1 (serialized: $s, unserialized: $v2)");
            }
        }
    }
}

ScalarSerializer::test();
print "done\n";