Add quoting to scalar variables

[kirillku]

Add quoting to scalar variables not to throw deprecation errors in Symfony 3.1

[pierre-tranchard]

How about merging @cleentfaar ?

[ondrejfuhrer]

@cleentfaar +1 for merging!

[ipecador]

@cleentfaar +1 for merging. Blocking future Symfony 4 migration

[elyanory]

+1 for merging.

[geoffrey-brier]

👍