[php-src] Issue #8073: Calling debug_backtrace in a foreach cycle restarts the foreach cycle

Issue: https://github.com/php/php-src/issues/8073 Comment Author: dstogov @cmb69 the difference between 7.2 and 7.3 is because of special handling of last element in 7.2 and below. In case you change first line to `$array = [1,2,3,4];` you'll get the same output. I would say that modification of array iterated through foreach by reference may cause undefined iteration behavior.