The foreach loop in PHP is designed for convenient iteration over arrays and collections (objects that can be traversed step by step). It is the simplest way to clearly process data in PHP programming: product lists, users, orders, query results, configuration arrays, etc. Unlike for, while, or do-while, foreach is specifically built for collections — it’s shorter, safer, and more understandable, especially for beginners.

Basics

What is foreach?

The foreach loop sequentially goes through each element of an array or iterable object and provides:

the value only, or
the key-value pair.

This means you don’t have to manually count indexes or check array length.

General syntax

Values only:

foreach ($collection as $value) {
    // use $value
}

Key and value:

foreach ($collection as $key => $value) {
    // use $key and $value
}

Iteration “by reference” (modifying elements in place):

foreach ($collection as &$value) {
    // modification changes the original element
}
unset($value); // important after using reference!

Foreach works on:

arrays (indexed and associative),
objects implementing Traversable (Iterator, IteratorAggregate),
generators (yield).

It does not work on non-iterable types like strings or ints (without conversion).

PHP Code Examples

Iterating over a simple array

<?php
$fruits = ['apple', 'banana', 'pear'];

foreach ($fruits as $fruit) {
    echo "Fruit: $fruit\n";
}

Iterating over an associative array (key => value)

<?php
$prices = [
    'bread' => 5.50,
    'milk'  => 3.20,
    'butter'=> 7.80,
];

foreach ($prices as $product => $price) {
    echo "Product: $product, price: " . number_format($price, 2) . " PLN\n";
}

Modifying array elements in place (reference)

<?php
$numbers = [1, 2, 3, 4];

foreach ($numbers as &$n) {
    $n *= 2;
}
unset($n); // important!

print_r($numbers); // [2, 4, 6, 8]

⚠️ Forgetting unset($n) may cause hard-to-find bugs.

Foreach with destructuring (list/\[])

<?php
$points = [
    [2, 3],
    [4, 1],
    [0, 5],
];

foreach ($points as [$x, $y]) {
    echo "Point: ($x, $y)\n";
}

$users = [
    ['id' => 1, 'name' => 'Ada'],
    ['id' => 2, 'name' => 'Bartek'],
];

foreach ($users as ['id' => $id, 'name' => $name]) {
    echo "User #$id: $name\n";
}

Iterating over an object (public properties)

<?php
$person = (object)[
    'name' => 'Jan',
    'age'  => 30,
];

foreach ($person as $property => $value) {
    echo "$property: $value\n";
}

Iterating over collections (Traversable, generators)

<?php
$collection = new ArrayObject(['a' => 10, 'b' => 20]);

foreach ($collection as $key => $value) {
    echo "$key = $value\n";
}

function evenUpTo(int $max): Generator {
    for ($i = 0; $i <= $max; $i++) {
        if ($i % 2 === 0) yield $i;
    }
}

foreach (evenUpTo(10) as $n) {
    echo "Even: $n\n";
}

Safe iteration with possibly null data

<?php
$maybeNull = null;

foreach ((array)$maybeNull as $el) {
    // won’t enter, no warnings
}

if (is_iterable($maybeNull)) {
    foreach ($maybeNull as $el) {}
} else {
    // handle non-iterable case
}

Flow control: continue and break

<?php
$products = [
    'bread' => 5.50,
    'milk'  => 3.20,
    'butter'=> 7.80,
];

foreach ($products as $name => $price) {
    if ($price > 7) {
        echo "Expensive: $name\n";
        continue;
    }

    if ($name === 'milk') {
        echo "Found milk, stopping.\n";
        break;
    }

    echo "OK: $name ($price)\n";
}

Nested foreach (array of arrays)

<?php
$orders = [
    ['id' => 1, 'items' => ['apple', 'banana']],
    ['id' => 2, 'items' => ['pear']],
];

foreach ($orders as $order) {
    echo "Order #{$order['id']}:\n";
    foreach ($order['items'] as $item) {
        echo "- $item\n";
    }
}

Practical example: summing values

<?php
$cart = [
    ['product' => 'pen', 'price' => 2.50, 'qty' => 3],
    ['product' => 'notebook', 'price' => 8.00, 'qty' => 2],
];

$total = 0.0;
foreach ($cart as $item) {
    $total += $item['price'] * $item['qty'];
}

echo "Total: " . number_format($total, 2) . " PLN\n";

Practical example: generating HTML list

<?php
$tasks = ['Clean windows', 'Write report', 'Call client'];

echo "<ul>\n";
foreach ($tasks as $task) {
    echo "  <li>" . htmlspecialchars($task, ENT_QUOTES, 'UTF-8') . "</li>\n";
}
echo "</ul>";

Modifying array during foreach

<?php
$numbers = [1, 2, 3];

foreach ($numbers as $n) {
    echo "$n\n";
    if ($n === 2) {
        $numbers[] = 4; // new element usually not visited in this loop
    }
}

⚠️ Foreach “plans” iteration at the start. Adding/removing elements usually doesn’t affect the current loop.

Best Practices and Common Mistakes

Best Practices

Prefer foreach for arrays/collections over for/while.
Use clear variable names: $user, $product, $row.
Use key-value form if key is meaningful.
Use references only when needed; always unset($ref) after.
Don’t resize arrays during foreach.
Use is_iterable or (array) for safety.
For large data sets, prefer generators (yield).
Use destructuring for readability when structure is known.

Common Mistakes

Forgetting unset($value) after reference iteration.
Iterating over non-iterable (e.g., string, int).
Expecting added elements to be visited immediately.
Trying reference on key (foreach ($arr as &$k => $v) → syntax error).
Assuming pointer functions (next/prev) affect foreach (they don’t).
Using for with arrays inefficiently (count() in condition repeatedly).

foreach vs other loops

for — best for numeric ranges and indexes.
while/do-while — best for unknown iterations.
foreach — best for arrays/collections; idiomatic in PHP.

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Summary

foreach is the main PHP loop for arrays/collections.
Syntax: foreach ($arr as $value) or foreach ($arr as $key => $value).
Use & for modifications, then unset reference.
Works with Traversable objects and generators.
Don’t resize arrays mid-loop.
Use destructuring for clarity.

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Mini Quiz

Syntax for foreach with key and value?

➡️ foreach ($arr as $key => $value) { ... }

Why use & in foreach? What to do after?

➡️ Modify originals; unset(\$value) after.

foreach on null?

➡️ Warning; fix with (array)$x or is_iterable($x).

Will added element be visited immediately?

➡️ Usually no.

How to destructure [x,y] arrays?

➡️ foreach ($points as [$x, $y])

What does foreach iterate on stdClass?

➡️ Public properties.

When use generators with foreach?

➡️ Large/streaming data.

Why is foreach better than for for arrays?

➡️ Clearer, avoids index/count issues.

Now you have solid foundations for the foreach loop in PHP. In your projects, choose foreach as the default tool for arrays and collections, applying the best practices above. You can revisit for, while, and do-while lessons to compare use cases.