问如何在Jenkinsfile中使用docker image内部环境变量？

EN

    stage('Run phpunit') {
      agent {
        docker { image 'php:7.2-alpine' }
      }
      steps {
        sh """
          apk add --no-cache ${PHPIZE_DEPS}
          pecl install xdebug
          docker-php-ext-enable xdebug
          php vendor/bin/phpunit --colors=never --log-junit build/junit.xml --coverage-clover build/clover.xml
        """
      }
    }

groovy.lang.MissingPropertyException: No such property: PHPIZE_DEPS for class: groovy.lang.Binding
at groovy.lang.Binding.getVariable(Binding.java:63)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onGetProperty(SandboxInterceptor.java:242)
at org.kohsuke.groovy.sandbox.impl.Checker$6.call(Checker.java:288)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedGetProperty(Checker.java:292)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedGetProperty(Checker.java:268)