How do I install XDebug on docker's official php-fpm-alpine image?

Question

I'm using wordpress:php7.1-fpm-alpine which is based on php:7.1-fpm-alpine (https://github.com/docker-library/wordpress/blob/master/php7.1/fpm-alpine/Dockerfile).

I've tried RUN pecl install xdebug-2.5.0 && docker-php-ext-enable xdebug

which results in an error when building:

Step 19/19 : RUN pecl install xdebug-2.5.0     && docker-php-ext-enable xdebug  ---> Running in 52c988e12cb2 downloading xdebug-2.5.0.tgz ... Starting to download xdebug-2.5.0.tgz (267,640 bytes) ........................................................done: 267,640 bytes 76 source files, building running: phpize Configuring for: PHP Api Version:         20160303 Zend Module Api No:      20160303 Zend Extension Api No:   320160303 Cannot find autoconf. Please check your autoconf installation and the $PHP_AUTOCONF environment variable. Then, rerun this script. 

Answer 1

The following is sufficient for simply installing xdebug on that image:

FROM wordpress:php7.1-fpm-alpine  RUN apk add --no-cache $PHPIZE_DEPS \     && pecl install xdebug-2.5.0 \     && docker-php-ext-enable xdebug 

Building that and then running from a shell inside the resulting image produces the following:

$ php -i | grep Xdebug     with Xdebug v2.5.0, Copyright (c) 2002-2016, by Derick Rethans