TL; DR

PECL をソースからビルドする必要があるのですが、それも面倒なので pecl コマンド入りのイメージを作成しました。Intel/AMD だけでなくラズパイなどの ARMv5,v7, ARM64 でも動作します。

docker pull keinos/php8-jit:latest

イメージ: keinos/php8-jit @ DockerHub
Dockerfile: keinos/php8-jit @ GitHub

$ docker run --rm keinos/php8-jit pecl version
PEAR Version: 1.10.12
PHP Version: 8.0.0-dev
Zend Engine Version: 4.0.0-dev
Running on: Linux 3fc54c34122a 4.19.76-linuxkit #1 SMP Tue May 26 11:42:35 UTC 2020 x86_64

また、PECL リポジトリのビルド済みパッケージで動かないものが多いので、PECL パッケージもソースからインストールできるようにしています。

要yaml-dev

docker-php-ext-pecl install yaml

TS; DR

Dockerfile

FROM keinos/php8-jit:latest

USER root

COPY sample.php /app/sample.php

RUN \
    apk --no-cache add yaml-dev && \
    docker-php-ext-pecl install yaml

ENTRYPOINT [ "php", "/app/sample.php" ]

sample.php

<?php

// YAML のサンプル文字列
$yaml = <<<EOD
---
invoice: 34843
date: "2001-01-23"
bill-to: &id001
  given: Chris
  family: Dumars
  address:
    lines: |-
      458 Walkman Dr.
              Suite #292
    city: Royal Oak
    state: MI
    postal: 48046
ship-to: *id001
product:
- sku: BL394D
  quantity: 4
  description: Basketball
  price: 450
- sku: BL4438H
  quantity: 1
  description: Super Hoop
  price: 2392
tax: 251.420000
total: 4443.520000
comments: Late afternoon is best. Backup contact is Nancy Billsmer @ 338-4338.
...
EOD;

// YAML 文字列を PHP 配列にパース
$parsed = yaml_parse($yaml);

// 比較テスト
$actual = json_encode($parsed);
$expect = '{"invoice":34843,"date":"2001-01-23","bill-to":{"given":"Chris","family":"Dumars","address":{"lines":"458 Walkman Dr.\n        Suite #292","city":"Royal Oak","state":"MI","postal":48046}},"ship-to":{"given":"Chris","family":"Dumars","address":{"lines":"458 Walkman Dr.\n        Suite #292","city":"Royal Oak","state":"MI","postal":48046}},"product":[{"sku":"BL394D","quantity":4,"description":"Basketball","price":450},{"sku":"BL4438H","quantity":1,"description":"Super Hoop","price":2392}],"tax":251.42,"total":4443.52,"comments":"Late afternoon is best. Backup contact is Nancy Billsmer @ 338-4338."}';

echo '- Function test ... ', ($expect === $actual) ? 'OK' : 'NG', PHP_EOL;

参考文献

Issue #846 PECL not working on php:7.4-rc-fpm-alpine3.9 | PHP @ docker-library @ GitHub
YAML @ PECL
インストール手順 | YAML @ PHP 公式マニュアル
yaml_parse | YAML 関数 | YAML @ PHP 公式マニュアル