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Introduction à PHP
Section 5. Chapitre 3
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Do-While

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The do-while and while loops are two types of loops in PHP used to repeat a block of code. However, there is a crucial difference between them: The while loop checks the condition before executing the code block, while the do-while loop checks the condition after completing the code block.

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It means that the while loop may not execute at all if the condition does not evaluate to true on the first check. On the other hand, the do-while loop will consistently execute at least once, even if the condition does not evaluate to true on the first check.

Syntax

We write commands that should work in a loop in the do block of code. This is the condition that determines whether to continue iterating the loop.

do {
 // code block
}
while (condition);

Let's create a loop with a condition that will never be true:

main.php

main.php


              
12345678

            
<?php
$counter = 5; // Declare and initialize the variable

do {
    echo 'Do-while loop';   
    $counter = $counter + 1;
} while ($counter == 5); // Change the condition to 5
?>

As you can see, the do-while loop executed the code block at least once, even if the condition counter != 0 was not evaluated to true on the first check.

Here is another way to understand the difference between the do-while and while loops:

  • The while loop is like checking before eating. You can only eat once you check if you are hungry;
  • The do-while loop is like eating before checking. You can eat, even if you are not hungry, and then check if you are still hungry.

Which type of loop to choose depends on your specific needs. Use a do-while loop if you want the code block to execute at least once. If you do not wish for the code block to run if the condition does not evaluate to true on the first check, use a while loop.

Tâche

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Fill in the blanks in the code to create a do-while loop that prints even numbers from 2 to 10.

  1. The variable number is already initialized with the value 2.
  2. Inside the do block, the code prints the current value of number.
  3. After printing, you need to increase number by 2 so that it moves to the next even number.
  4. In the while condition, make sure the loop continues as long as number is less than or equal to 10.

Solution

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Section 5. Chapitre 3
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