php apm agent error - Elastic\Apm\Impl\getmypid()

[mohammadalipour]

APM Server version (apm-server version): 8.7.2

Description of the problem including expected versus actual behavior:
PHP-APM-agent 1.9.1 is installed on the php-alpine image (PHP version 8.1) on the AWS ECS machine

Provide logs (if relevant):
and get this error :

[Elastic APM PHP Tracer][CRITICAL] [Bootstrap] [BootstrapStageLogger.php:225] [callAndSwallowThrowable] Handling shutdown call let a throwable escape - skipping the rest of the steps. Error: Call to undefined function Elastic\Apm\Impl\getmypid()

[dmathieu]

That seems like an issue for https://github.com/elastic/apm-agent-php?