Arrays

By the end of this lesson you'll store many values in one variable — ordered lists, key-value records, and nested tables — and reshape them at will with PHP's array functions, the everyday workhorse of real applications.

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Part of the free Php course at LearnCodingFast — hands-on lessons with examples you run in your browser, plus practice exercises and a quick quiz.

What You'll Learn in This Lesson

1️⃣ Indexed Arrays — Ordered Lists

An array is a single variable that holds many values. The simplest kind is an indexed array — an ordered list where PHP labels each slot with a number starting at 0 , not 1. You create one with the modern short syntax [ ] (older code uses array(...) — same thing). You read a slot by its index, and you tack a value onto the end with the handy $array[] = ... shortcut, which lets PHP pick the next number for you.

2️⃣ Associative Arrays — Key → Value

When position isn't meaningful but a label is, use an associative array . Instead of numbers, you choose your own keys — usually strings — and pair each with a value using the => arrow (read it as "points to"). This is how PHP models a record: a user, a config setting, a row from a database. You look values up by key, and assigning to a new key adds it while assigning to an existing key overwrites it.

Notice the {' $person['name'] '} trick: inside a double-quoted string, wrapping an array lookup in curly braces lets PHP drop the value in cleanly. Without the braces, "$person['name']" confuses the parser.

3️⃣ Multidimensional Arrays & foreach

Because an array's values can themselves be arrays, you can build tables and nested structures — a list of records, a grid, JSON-shaped data. To walk through any array, reach for foreach : it hands you each element in turn without you tracking an index. To reach a nested value, stack the brackets: outer position, then inner key.

4️⃣ Adding & Removing Items

Arrays are not fixed in size — you grow and shrink them as the program runs. Append with the $a[] = shortcut or array_push (which can add several at once); add to the front with array_unshift . Remove and capture the last item with array_pop or the first with array_shift . To delete one specific element by key, use unset — but note it leaves a gap in the numbering rather than renumbering.

5️⃣ Transforming Data — map, filter, reduce

The real power of PHP arrays is its library of built-in functions. Three are worth learning by heart. array_map applies a function to every element and returns a new array. array_filter keeps only the elements your test returns true for. array_reduce boils the whole array down to a single value (a sum, a max, a joined string). Watch the argument order — array_map(fn, array) but array_filter(array, fn) . Alongside them, in_array , array_keys , array_values , and the string pair implode / explode cover most everyday needs.

Now you try. The script below is almost complete — fill in each ___ using the 👉 hint, then run it and check it against the Output panel.

6️⃣ Sorting, Merging & Unpacking

sort reorders an indexed list ascending — but it renumbers the keys , so on an associative array it would throw your labels away. For keyed data use asort (by value) or ksort (by key); for a custom rule use usort with a comparison function. To combine arrays, use array_merge or the newer spread operator ... ; and list() destructuring — written as [$x, $y] = [...] — unpacks an array straight into separate variables.

One more. Build a small contact card as an associative array, then loop it with foreach ($arr as $key => $value) , which hands you both halves of each pair.

📋 Quick Reference — PHP Arrays

No code is filled in this time — just a brief and an outline. Write it yourself, run it on onecompiler.com/php or your own machine, then check your result against the expected output in the comments. This combines array_filter , usort , foreach and array_reduce — the real toolkit.

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