Concatenation precedence

[i582]

RFC: https://wiki.php.net/rfc/concatenation_precedence

See: https://github.com/php/php-src/pull/4002/files

Example:

echo "sum: " . $a + $b;

// PHP would previously interpret it like this:
echo ("sum: " . $a) + $b;

// PHP 8 will make it so that it's interpreted like this:
echo "sum: " . ($a + $b);