Loops

Introduction

Loops let you repeat a block of code without writing it out multiple times — printing a list of products, processing every row from a database, or retrying an operation until it succeeds. PHP provides four loop constructs, each suited to slightly different situations.

In this lesson you will learn for, while, do-while, and foreach, including how foreach can access both keys and values, how to nest loops inside one another, and how the four loop types compare when solving the exact same task.

The for Loop

A for loop is ideal when you know in advance how many times you want to repeat something. It packs initialization, condition, and increment into one line: for (initialization; condition; increment).

<?php
for ($i = 1; $i <= 5; $i++) {
    echo "Count: $i\n";
}

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

The loop starts by setting $i to 1, checks the condition ($i <= 5) before every iteration, runs the body if true, then increments $i and checks again — repeating until the condition becomes false.

The while Loop

A while loop repeats its body as long as its condition remains true. It checks the condition before each iteration, so if the condition starts out false, the body never runs at all.

<?php
$i = 1;

while ($i <= 5) {
    echo "Count: $i\n";
    $i++;
}

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

The do-while Loop

A do-while loop is like while, but it checks the condition after the body runs instead of before. That guarantees the body executes at least once, even if the condition is false from the very start.

<?php
$i = 10;

do {
    echo "Runs once even though condition is false: $i\n";
    $i++;
} while ($i < 5);

Runs once even though condition is false: 10

Even though $i < 5 is false immediately (10 is not less than 5), the body still runs one time before the condition is checked. This makes do-while useful for things like showing a menu at least once before checking whether the user wants to exit.

The foreach Loop

foreach is built specifically for iterating over arrays (and other iterable structures), so you never have to manage an index counter manually.

<?php
$fruits = ["Apple", "Banana", "Cherry"];

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

I like Apple
I like Banana
I like Cherry

When you also need the key (the index for a plain array, or the key for an associative array), use the as $key => $value form.

<?php
$prices = [
    "Coffee" => 3.50,
    "Tea" => 2.75,
    "Juice" => 4.00,
];

foreach ($prices as $item => $price) {
    echo "$item costs \$$price\n";
}

Coffee costs $3.5
Tea costs $2.75
Juice costs $4

Nested Loops

A loop can contain another loop inside it — useful for working with grids, tables, or combinations of two lists. The inner loop completes all of its iterations for every single iteration of the outer loop.

<?php
for ($row = 1; $row <= 3; $row++) {
    for ($col = 1; $col <= 3; $col++) {
        echo "($row,$col) ";
    }
    echo "\n";
}

(1,1) (1,2) (1,3) 
(2,1) (2,2) (2,3) 
(3,1) (3,2) (3,3)

This pattern is common for generating multiplication tables, rendering grid-based layouts, or comparing every item in one list against every item in another.

Comparing All Four Loops

To see how similar these constructs really are, here is the exact same task — printing the numbers 1 through 3 — written with each loop type.

<?php
// for
for ($i = 1; $i <= 3; $i++) {
    echo $i . " ";
}

1 2 3 

<?php
// while
$i = 1;
while ($i <= 3) {
    echo $i . " ";
    $i++;
}

1 2 3 

<?php
// do-while
$i = 1;
do {
    echo $i . " ";
    $i++;
} while ($i <= 3);

1 2 3 

<?php
// foreach
foreach ([1, 2, 3] as $i) {
    echo $i . " ";
}

1 2 3 

All four produce identical output here, but they fit different situations: for suits a known range, while and do-while suit condition-driven repetition, and foreach is the natural choice whenever you already have an array to walk through.

Common Mistakes

Best Practices

Frequently Asked Questions

Key Takeaways

Summary

Loops are the foundation of repeating work in PHP. You now know all four loop constructs, when each one fits best, how foreach handles keys and values, and how loops can be nested to handle multi-dimensional problems.