Added note about array_merge php function
minor #1487 Added note about array_merge php function (pulzarraider)

This PR was merged into the 1.16-dev branch.

Discussion
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Added note about array_merge php function

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT

Just a small doc improvement.

Commits
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f712b8f Added note about array_merge php function