nice answer. I can tell you what happen if you run 1,000,000 iterations based on loop – this will take about 72 MB in 1.13 s.

I have investigated the memory usage too, but the differences was too small to talk about this and was caused by using objects against simple arrays. Why the SPL Iterator’s code shows you so low memory usage? Because the memory is freed just after the last foreach. It works in the same way as in the case where you put all the code from http://codepad.viper-7.com/k68YS6 into function like this: https://gist.github.com/piotrpasich/857cd0e4a0988e11a5f4 . At the result, the memory usage is 0.58746337890625 KB.

So, the place where you measure the memory matters.

Thank you for the comment,
Piotr

However, you skipped over probably the best reason to use iterators, which is the efficiencies gained in memory.

I tested your code (with some slight modifications for running online vs the command line) on PHP 5.6.1 & added measurements for memory usage.

Code using loops:
100,000 iterations – http://codepad.viper-7.com/k68YS6
Duration: 0.095134973526001
Memory: 0.296875 KB

1,000,000 iterations – The script ran out of memory in the REPL environment while generating the first array

Code using Iterators
100,000 iterations – http://codepad.viper-7.com/ptauX3
Duration: 0.21263003349304
Memory: 2.15625 KB

1,000,000 iterations – http://codepad.viper-7.com/m3cNIy
Duration: 2.1547520160675
Memory: 2.15625 KB

As you can see, you see the same marked increase in time from using loops to using iterators for the 100k iteration test. Memory usage is also more. However, in the iterators test going increasing the iterations by an order of magnitude increased the duration by an order of magnitude as well, but the memory usage remained constant. Increasing another order of magnitude would increase the duration as well, but memory usage wouldn’t go up much more than the 2.2 KB being used by the script.

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