Symfony version(s) affected: all ?

Description
The PhpMatcherDumper::export method creates invalid code when a route attribute is an object.

How to reproduce

In symfony repository, run :

php -r 'include __DIR__."/vendor/autoload.php"; class A { private $a; }; $export = \Symfony\Component\Routing\Matcher\Dumper\PhpMatcherDumper::export(new A); echo "$export\n"; eval("${export};");'

And it will produce

A::__set_state(array('."\n".'   'a' => NULL,'."\n".'))

PHP Parse error:  syntax error, unexpected ''a'' (T_CONSTANT_ENCAPSED_STRING), expecting ')' in Command line code(1) : eval()'d code on line 1

Possible Solution

A patch is available here and a pull request can be done.

The patch might break the formatting rules inside the export method, and I don't know why it's there.

Additional context
I don't know if the patch is a good idea, because a lot of solutions exist to deal with the issue :

• serialize the object (using serialize or var_export) before setting the attribute to the route, thus setting it to a string value ;
• use a reference and get the value in a cache pool or provider service ;
• the object creation at each request might not be a good idea for mem/cpu perfs ‒ that's why I preferred to use another way to get my object, only when needed.