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array-functions

Essential array functions

Last reviewed May 28, 2026 Content v20260528
Track mode
server_script
Means
Server runner
Reading
~1 min
Level
intermediate

This lesson

This lesson teaches Essential array functions: the syntax, APIs, and habits you need before advancing in PHP.

Functions keep scripts maintainable before you reach for classes and frameworks.

You will apply Essential array functions in contexts like: LAMP/LEMP stacks, Laravel apps, WordPress themes/plugins, and shared hosting.

Write PHP in the editor and click Run on server—the dev runner executes your script and returns stdout/stderr (set LEARNING_RUNNER_ENABLED=true locally).

When you can explain the previous lesson's ideas without copying starter code.

PHP ships dozens of array helpers. Learn the ones you will reach for daily before memorizing edge cases.

Transform and filter

  • array_map(fn($x) => ..., $arr) — transform each element
  • array_filter($arr, fn($x) => ...) — keep matching elements
  • array_reduce — fold to a single value

Search and sort

  • in_array($needle, $haystack, true) — strict third arg recommended
  • array_search, sort, asort, ksort

Combine and slice

array_merge, array_slice, array_column (extract one field from rows), array_unique.

Self-check

  1. Why pass true as the third argument to in_array?
  2. Which function extracts all email keys from an array of users?

Interview tip Lesson completion confidence

Can you explain this lesson in 30 seconds without reading notes?

Not saved yet.

Playground

Runs on the configured server runner (dev: npm run runner with LEARNING_RUNNER_ENABLED=true). Output appears below the editor.

Check yourself

Multiple choice — immediate feedback.

Discussion

Past discussion is visible to everyone. Only logged-in users can post comments and replies.

Starter discussion topics

  • map filter reduce?
  • sort stable how?

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