ExampleVm.php

<?php
/**
 * Class ExampleVm
 */
class ExampleVm
{
    public const OP_ALLOC      = 0x00;
    public const OP_ADD        = 0x01;
    public const OP_GOTO       = 0x02;
    public const OP_ASSERT     = 0x03;
    public const OP_ASSERT_LTE = 0x04;
    public const OP_INC        = 0x05;
    public const OP_ECHO       = 0x06;

    public array $symbols = [];

    public function run(array $program): void
    {
        for ($state = 0, $len = \count($program); $state < $len; ++$state) {
            [$code, $args] = $program[$state];

            switch ($code) {
                case self::OP_ALLOC:
                    $this->symbols[$args[0]] = $args[1];
                    break;

                case self::OP_INC:
                    ++$this->symbols[$args[0]];
                    break;

                case self::OP_ADD:
                    if (\is_array($this->symbols[$args[0]])) {
                        $this->symbols[$args[0]][] = $this->symbols[$args[1]];
                        break;
                    }
                    throw new \RuntimeException('Bad type');

                case self::OP_GOTO:
                    $state = ($args[0] - 1);
                    break;

                case self::OP_ASSERT:
                    if (! $this->symbols[$args[0]]) {
                        $state = $args[1];
                    }
                    break;

                case self::OP_ASSERT_LTE:
                    if ($this->symbols[$args[0]] > $args[1]) {
                        $state = $args[1];
                    }
                    break;

                case self::OP_ECHO:
                    echo $this->symbols[$args[0]];
                    break;
            }
        }
    }
}

executor.php

<?php
$vm = new ExampleVm();

$before = \microtime(true);

$vm->run([
    0 => [ExampleVm::OP_ALLOC, ['a', []]],
    1 => [ExampleVm::OP_ALLOC, ['i', 0]],
    2 => [ExampleVm::OP_ASSERT_LTE, ['i', 1000, 99]],
    3 => [ExampleVm::OP_ADD, ['a', 'i']],
    4 => [ExampleVm::OP_INC, ['i']],
    5 => [ExampleVm::OP_GOTO, [2]],
    6 => [ExampleVm::OP_ECHO, ['i']],
]);


echo number_format(\microtime(true) - $before, 6) . 's';
// 0.000354s