Loops in PHP

PHP has four loop constructs, and picking the right one mostly comes down to whether you're counting, checking a condition, or iterating over a collection.

for: when you know how many times to loop

<?php
for ($i = 0; $i < 5; $i++) {
    echo "Iteration $i\n";
}

The three parts — initialization, condition, increment — run in that order: set $i once, check the condition before every iteration, and run the increment after every iteration's body. for is the natural fit whenever a loop is driven by a counter.

while: loop while a condition holds

<?php
$attempts = 0;

while ($attempts < 3) {
    echo "Attempt " . ($attempts + 1) . "\n";
    $attempts++;
}

The condition is checked before each iteration, including the first — if it's false immediately, the loop body never runs at all.

do-while: guarantee at least one run

<?php
$input = "";

do {
    $input = readInput();
} while ($input === "");

do-while checks its condition after the body runs, guaranteeing at least one iteration regardless of the condition's initial value — useful for something like "keep asking until we get valid input," where you need to ask at least once before there's anything to check.

foreach: the standard way to loop over an array

<?php
$fruits = ["apple", "banana", "cherry"];

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

$user = ["name" => "Amara", "role" => "admin"];

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

foreach is by far the most common loop in everyday PHP — it iterates directly over an array's values (or, with as $key => $value, both keys and values) without needing to manage an index counter yourself. It works on both indexed and associative arrays identically.

break and continue

<?php
foreach ($fruits as $fruit) {
    if ($fruit === "banana") {
        continue; // skip this iteration
    }
    if ($fruit === "cherry") {
        break; // stop the loop entirely
    }
    echo $fruit;
}

continue skips the rest of the current iteration and moves to the next one; break exits the loop immediately, skipping any remaining iterations. Both work in every loop type covered in this lesson.

Modifying an array while looping over it by reference

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

foreach ($numbers as &$number) {
    $number *= 2;
}
unset($number); // break the reference after the loop

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

&$number makes $number a reference to each array element rather than a copy, so modifying it inside the loop modifies the original array. Always unset() the reference variable immediately after a foreach that uses & — leaving it alive is a well-known source of subtle bugs if the same variable name is reused in a later loop.