PHP array_merge 与 foreach 循环

Question

I was working on a Laravel project. Where I had to marge 3 arrays. Array sizes may be big or empty. Firstly my concept was using

array_merge($first_array, $second_array, $third_array)

FYI array has only numbers. One array element may belong to another array. I don't need to remove duplicates or sort arrays. But it is mandatory that the first array data must be first on merged_array.

Somehow it wasn't performing well. Then I wrote this code there.

foreach ($array2 as $i) { $array1[] = $i; }

Now my curiosity is which code is faster or efficient. With large data or less data.

My experience with

• 10k data (sum of 3 arrays)
• 1k data (sum of 3 arrays)

Results

• 1 no results

  • array_merge takes time of n
  • foreach takes time of sqrt(n)

• 2 no results

  • array_merge takes time of n
  • foreach takes time of n^2

Answer 1

Actually it depends on server PC config. When server PC RAM is free (no cache), it works fine. otherwise it don't show real answer (time complexity). I had found my own answer later.