Left-associative ternary operator deprecation https://wiki.php.net/rfc/ternary_associativity. The ternary operator has some weird quirks in PHP. This RFC adds a deprecation warning for nested ternary statements. In PHP 8, this deprecation will be converted to a compile time error.
1 ? 2 : 3 ? 4 : 5; // deprecated
(1 ? 2 : 3) ? 4 : 5; // ok
source: https://stitcher.io/blog/new-in-php-74#numeric-literal-separator-rfc