PSR12 php-cs-fixer config

.php_cs.php

<?php

$finder = PhpCsFixer\Finder::create()
    ->exclude('somedir')
    ->notPath('src/Symfony/Component/Translation/Tests/fixtures/resources.php')
    ->in(__DIR__)
;

return PhpCsFixer\Config::create()
    ->setRules([
    '@PSR2' => true,
    'blank_line_after_opening_tag' => true,
    'braces' => ['allow_single_line_closure' => true],
    'compact_nullable_typehint' => true,
    'concat_space' => ['spacing' => 'one'],
    'declare_equal_normalize' => ['space' => 'none'],
    'function_typehint_space' => true,
    'new_with_braces' => true,
    'method_argument_space' => ['on_multiline' => 'ensure_fully_multiline'],
    'no_empty_statement' => true,
    'no_leading_import_slash' => true,
    'no_leading_namespace_whitespace' => true,
    'no_whitespace_in_blank_line' => true,
    'return_type_declaration' => ['space_before' => 'none'],
    'single_trait_insert_per_statement' => true,
])
    ->setFinder($finder);

Borrowed the rules from PHP-CS-Fixer/PHP-CS-Fixer#4502 (comment)