PHP:What is faster? array_merge or array union operator (+)?

Question

I have two arrays with unique numeric keys. How can I merge them faster?

Answer 1

10000000 iterations on PHP 7.1.5 with two small multi-dimensional arrays:

• plus-operator (+): 1.966 seconds
• array_merge: 9.431 seconds

So the plus operator is faster but if you have collisions, the result is different.