PHP Loops: The Power of Repetition

PHP loops. How to repeat a block of code without writing it out again and again.

Understanding loops in PHP

Loops run the same block of code repeatedly while a condition holds. PHP has several loop types, each suited to slightly different situations.

The while loop

A while loop checks its condition first, then runs the code block if the condition is true:

<?php
$counter = 1;

while ($counter <= 5) {
    echo "Loop iteration: $counter <br>";
    $counter++;
}
?>

This runs five times, printing the counter value each time.

The do...while loop

A do...while loop runs its body once before checking the condition, so the code inside always executes at least once:

<?php
$counter = 1;

do {
    echo "Loop iteration: $counter <br>";
    $counter++;
} while ($counter <= 5);
?>

Even if $counter starts above 5, the loop body still runs once.

The for loop

Use a for loop when you know exactly how many iterations you need. Initialisation, condition, and increment all sit on one line:

<?php
for ($counter = 1; $counter <= 5; $counter++) {
    echo "Loop iteration: $counter <br>";
}
?>

The foreach loop

foreach is the easiest way to loop through an array:

<?php
$colors = array("red", "green", "blue", "yellow");

foreach ($colors as $color) {
    echo "Color: $color <br>";
}
?>

Each colour is printed in turn.

Breaking out of loops

Use break to exit a loop early:

<?php
for ($counter = 1; $counter <= 10; $counter++) {
    if ($counter == 6) {
        break;
    }
    echo "Loop iteration: $counter <br>";
}
?>

The loop stops when $counter reaches 6.

Skipping iterations with continue

Use continue to skip the rest of the current iteration and move to the next:

<?php
for ($counter = 1; $counter <= 5; $counter++) {
    if ($counter == 3) {
        continue;
    }
    echo "Loop iteration: $counter <br>";
}
?>

The number 3 is skipped in the output.

Nested loops

You can put a loop inside another loop. Nested loops are useful for multidimensional arrays and building grid-like output:

<?php
for ($i = 1; $i <= 3; $i++) {
    for ($j = 1; $j <= 3; $j++) {
        echo "$i - $j <br>";
    }
}
?>

This prints every combination of $i and $j.

Practical example: creating a table

Nested loops are a common way to generate HTML tables:

<?php
echo "<table border='1'>";
for ($row = 1; $row <= 5; $row++) {
    echo "<tr>";
    for ($col = 1; $col <= 5; $col++) {
        echo "<td>Row $row - Column $col</td>";
    }
    echo "</tr>";
}
echo "</table>";
?>

This builds a 5×5 HTML table – a good test that your nested loops are working.

Loops save you from writing the same code repeatedly. The table example is worth typing out yourself. Next up: functions – reusable blocks of code you can call from anywhere in your script.