Foreach could always produce infinite loops. Both through iterators (InfiniteIterator), but also for arrays. The modifications you had to do were only different previously.

If you don't want an infinite loop, don't grow your array infinitely...

PHP 5.3 - PHP 5.6 would use a copy of the array, thus not producing an infinite loop. The change in behaviour is the concern here.

PHP 5 would not create a copy for by-reference iteration. That's pretty much the point of iterating by-reference, that you're working on the original array, not a copy of it. The foreach implementation in PHP 5 was simply broken and didn't handle this particular case correctly. With a slight change to your sample code you'll get an infinite loop in PHP 5 as well: https://3v4l.org/FX3Ld (Two starting elements instead of one)

The foreach changes in PHP 7 are specified here: https://wiki.php.net/rfc/php7_foreach

Thanks nikic. 

I didn't suggest PHP created a copy of the array for by-reference iteration. I suggested that there's a change in behaviour because foreach in PHP 7 defaults to by-reference iteration, not creating a copy of the array and iterating over said copy.

You've already pointed out this fixes a broken implementation.