[php-src] Issue #8296: Numeric casts show emit a warning it they do not make sense

Issue: https://github.com/php/php-src/issues/8296 Author: mvorisek ### Description ``` (float) '1'; (float) '1.0'; (float) ''; (float) 'x'; // should always warn (int) '1'; (int) '1.0'; (int) ''; (int) 'x'; // should always warn ``` https://3v4l.org/gDLOv This is a feature request. The casts above are advised by many static analysers, but if added explicitly, there is currently no warning emit. They should at least emit a warning if the input is not numerical and the cast does not make sense.