Mark a service as a consumer of others via tags and extension

readme.md

1. Mark your service as a consumer with the tag "xphere.tag_collection"
2. Define the apply-to attribute, which defines the tag to be consumed
3. Declare the method attribute, is the one that will be called on every tag found
4. Mark your services to be consumed with the tag defined in the apply-to attribute
5. Automatical injection! :D

example.xml

<?xml version="1.0" ?>

<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">
    <parameters>
        <parameter key="xphere.chain.class">xPheRe\Bundle\TestBundle\Model\Chain</parameter>
        <parameter key="xphere.link.class">xPheRe\Bundle\TestBundle\Model\Link</parameter>
    </parameters>
    <services>
        <service id="xphere.chain" class="%xphere.chain.class%">
            <argument>Root</argument>
            <tag name="xphere.tag_collection" apply-to="xphere.tag.chain_to_root" method="addLink" />
        </service>
        <service id="xphere.chain.link_1" class="%xphere.link.class%">
            <argument>First</argument>
            <tag name="xphere.tag.chain_to_root" />
        </service>
        <service id="xphere.chain.link_2" class="%xphere.chain.class%">
            <argument>Second</argument>
            <tag name="xphere.tag.chain_to_root" />
            <tag name="xphere.tag_collection" apply-to="xphere.tag.chain_to_second" method="addLink" />
        </service>
        <service id="xphere.chain.link_3" class="%xphere.link.class%">
            <argument>Third</argument>
            <tag name="xphere.tag.chain_to_root" />
        </service>
        <service id="xphere.chain.link_4" class="%xphere.link.class%">
            <argument>Fourth</argument>
            <tag name="xphere.tag.chain_to_root" />
            <tag name="xphere.tag.chain_to_second" />
        </service>
    </services>
</container>

TagBundle.php

<?php

namespace xPheRe\Bundle\TagBundle;

use Symfony\Component\HttpKernel\Bundle\Bundle;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use xPheRe\Bundle\TagBundle\DependencyInjection\Compiler\TagCollectionPass;

class xPheReTagBundle extends Bundle
{
    public function build(ContainerBuilder $container)
    {
        parent::build($container);

        $container->addCompilerPass(new TagCollectionPass());
    }
}

TagCollectionPass.php

<?php

namespace xPheRe\Bundle\TagBundle\DependencyInjection\Compiler;

use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Reference;

class TagCollectionPass implements CompilerPassInterface
{
    public function process(ContainerBuilder $container)
    {
        foreach ($container->findTaggedServiceIds('xphere.tag_collection') as $service => $tags) {
            $definition = $container->getDefinition($service);
            foreach ($tags as $attributes) {
                $tag = $attributes['apply-to'];
                $method = $attributes['method'];
                foreach ($container->findTaggedServiceIds($tag) as $subservice => $subtags) {
                    $definition->addMethodCall($method, array(new Reference($subservice)));
                }
            }
        }
    }
}

This has evolved into its own bundle.
Go see xphere/tag-bundle for more features.
composer require xphere/tag-bundle