PHP-CS-Fixer/.composer-require-checker.json

{
    "symbol-whitelist" : [
        "Symfony\\Component\\EventDispatcher\\Event",
        "Symfony\\Contracts\\EventDispatcher\\Event",
        "Symfony\\Contracts\\EventDispatcher\\EventDispatcherInterface",

        "null", "true", "false",
        "static", "self", "parent",
        "array", "string", "int", "float", "bool", "iterable", "callable", "void",
        "T_AMPERSAND_FOLLOWED_BY_VAR_OR_VARARG",
        "T_AMPERSAND_NOT_FOLLOWED_BY_VAR_OR_VARARG",
        "T_ATTRIBUTE",
        "T_COALESCE_EQUAL",
        "T_ENUM",
        "T_FN",
        "T_MATCH",
        "T_NAME_FULLY_QUALIFIED",
        "T_NAME_QUALIFIED",
        "T_NAME_RELATIVE",
        "T_NULLSAFE_OBJECT_OPERATOR",
        "T_READONLY"
    ],
    "php-core-extensions" : [
        "dom", "mbstring", "Phar",
        "Core", "date", "pcre", "Reflection", "SPL", "standard"
    ]
}