Install it

composer require jdecool/twig-constant-accessor-bundle

<?phpreturn [// ...JDecool\Bundle\TwigConstantAccessorBundle\JDecoolTwigConstantAccessorBundle::class => ['all' =>true],];

twig_constant_accessor:classes:        -AppBundle\Model\Foo        -{ class: 'AppBundle\Model\Bar' }        -{ class: 'AppBundle\Model\FooBar', alias: 'FooBarAlias' }        -{ class: 'AppBundle\Model\ConstantClass', matches: '/^RULE_/' }# matches accept an regexp compatible with the preg_match function

services:my_service:class:Namespace\To\ServiceClasstags:            -{ name: twig.constant_accessor }my_collection:class:MyClasstags:            -{ name: twig.constant_accessor, alias: 'MyClassAlias' }filtered_constants:class:ConstantsClasstags:            -{ name: twig.constant_accessor, matches: '/^RULE_/' }# matches accept an regexp compatible with the preg_match function

useJDecool\Bundle\TwigConstantAccessorBundle\Annotation\AsTwigConstantAccessor;#[AsTwigConstantAccessor]class MyClass{// ...}

{{ServiceClass.MY_CONSTANT }}{{MyClassAlias.KEY }}{%if'value'==ServiceClass.My_CONSTANT %}Test is OK{%endif %}