Is it required to keep space after type cast by Symfony coding standards?
Yes, it is:
How to Apply It?
In CodeSniffer, you're looking for
PHP_CodeSniffer\Standards\Generic\Sniffs\Formatting\SpaceAfterCastSniff
In PHP-CS-Fixer, it would be
PhpCsFixer\Fixer\CastNotation\CastSpacesFixer
Tool used in here is EasyCodingStandard - you can read intro post about it.