PHP while Loop and do while: Syntax and Examples

while (condition) { ... } runs the block again and again as long as the condition is true. The condition is checked before every pass, so if it is false from the start, the body never runs. Something inside the loop has to change the condition, or it never ends.

<?php
$balance = 1000;
$year = 0;

while ($balance < 2000) {
    $balance *= 1.07;   // 7% interest per year
    $year++;
}

echo "Doubled after $year years: ", round($balance, 2);

This is the kind of question while is made for: you do not know the number of passes in advance, only when to stop. Change the interest rate and run it again.

do while: run at least once

do { ... } while (condition); checks the condition after the body, so the body always runs once. Note the semicolon at the end.

<?php
$i = 10;

while ($i < 5) {
    echo "while: $i\n";   // never runs
    $i++;
}

$i = 10;
do {
    echo "do while: $i\n"; // runs once
    $i++;
} while ($i < 5);

A typical use is "try, then check": roll a die until you get a six, generate a code until it is unused. The first attempt has to happen before there is anything to check. This one gives a different result every run:

<?php
$rolls = 0;

do {
    $roll = random_int(1, 6);
    $rolls++;
    echo "Roll $rolls: $roll\n";
} while ($roll !== 6);

echo "Got a six after $rolls rolls\n";

while (true) with break

When the exit condition is easier to check in the middle of the body, write while (true) and leave with break. continue skips to the next check, as in any loop.

<?php
$queue = ['email:ada', 'skip', 'email:linus', 'stop', 'email:grace'];

while (true) {
    $job = array_shift($queue);   // take the first item

    if ($job === null) {
        echo "Queue empty\n";
        break;
    }
    if ($job === 'skip') {
        continue;
    }
    if ($job === 'stop') {
        echo "Stop signal, ", count($queue), " job(s) left\n";
        break;
    }

    echo "Processing $job\n";
}

array_shift() returns null once the array is empty, which is the other way out. The same loop could be written as while ($queue), because an empty array counts as false.

Read a file line by line

fgets() returns one line at a time and false at the end of the file, so it drives a while loop directly. The block writes the file first, then reads it back.

<?php
file_put_contents('visits.log', "2026-03-01 home\n2026-03-01 pricing\n2026-03-02 home\n");

$handle = fopen('visits.log', 'r');
$count = 0;

while (($line = fgets($handle)) !== false) {
    $count++;
    [$date, $page] = explode(' ', trim($line));
    echo "$count: $page on $date\n";
}

fclose($handle);

The parentheses around $line = fgets($handle) matter: the assignment happens first, then the result is compared with false. Using !== false instead of a plain truthy check keeps a last line that holds just 0 (with no newline after it) from ending the loop early. The fopen() page covers the file functions.

while with endwhile in templates

Like if and for, while has a colon form for HTML: while (...): and endwhile;. This one prints a countdown list in the Page tab.

<?php
$n = 5;
?>
<ol reversed>
<?php while ($n > 0): ?>
    <li><?= $n ?> second<?= $n === 1 ? '' : 's' ?> left</li>
    <?php $n--; ?>
<?php endwhile; ?>
</ol>
<p>Done.</p>

Common mistake: the loop that never ends

The counter has to move toward the exit. Forget $i++, or change the wrong variable, and the condition stays true forever. On a web server PHP stops the script after max_execution_time (30 seconds by default) with a fatal error. On the command line it never stops.

// Never ends: $i is never changed
$i = 0;
while ($i < 3) {
    echo $i;
}

A safety limit is a cheap guard for loops that depend on outside data, such as retrying a call or paging through results:

<?php
$attempt = 0;
$maxAttempts = 5;
$success = false;

while (!$success && $attempt < $maxAttempts) {
    $attempt++;
    $success = random_int(1, 4) === 1;   // pretend this is a network call
    echo "Attempt $attempt: ", $success ? "ok" : "failed", "\n";
}

echo $success ? "Done\n" : "Gave up after $maxAttempts attempts\n";

Run it a few times: sometimes it succeeds early, sometimes it gives up, but it always ends. When you know the number of passes up front, a for loop states the start, end and step in one line and is harder to get wrong.