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PHP While Loop

A while loop repeats a block of code while its test stays true. PHP also has a do-while loop, and that form runs its block once before its first test.

Counting up with while

The counter starts at 1. Each round prints the counter and adds 1 to it.

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

Counting down with while

The counter starts at 3. Each round prints the counter and takes 1 away from it.

<?php
$i = 3;
while ($i >= 1) {
  echo $i . "\n";
  $i--;
}

A do-while loop runs once

The counter holds 10, so the test is false from the start. The block still prints its one line.

<?php
$i = 10;
do {
  echo $i . "\n";
} while ($i < 5);

Example

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

Key points

  • A while loop tests its condition before each round.
  • The block runs again and again while the test stays true.
  • A counter often changes inside the block so the test can turn false.
  • A do-while loop writes its block before its while test.
  • A do-while loop tests at the end, so the block runs at least once.

In this example, the counter starts at 1. The first round prints 3 times 1, which is 3. The next rounds print 6 and 9, and the counter then ends the loop.

Note

A test that never turns false makes a loop run without end.

Try it Yourself

Edit the code, then press Run.

Running is simulated · Programiz PHP Compiler

Exercise

A do-while loop has a test that is false from the start. How many times does its block run?