PHP Do-While loop

The basic syntax of "Do-While" Loop in PHP is as follows:

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do {
   // Code to be executed at least once
} while (condition);
 

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$valid = false;
do {
    $userInput = readline("Enter a valid number: ");
    if (is_numeric($userInput)) {
        $valid = true;
    } else {
        echo "Invalid input. Please enter a valid number.\n";
    }
} while (!$valid);

echo "You entered a valid number: " . $userInput;
 

• In this example, we use a do-while loop to repeatedly prompt the user for input until they enter a valid number.
• The $valid variable is initially set to false.
• The code inside the loop block asks the user for input using readline(), checks if it's numeric using is_numeric(), and sets $valid to true if the input is valid.
• If the input is invalid, an error message is displayed, and the loop continues.
• The loop continues executing until $valid becomes true, ensuring the user enters a valid number.

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$roll = 0;

do {
    $roll = rand(1, 6);
    echo "Rolled a $roll.\n";
} while ($roll != 6);

echo "You rolled a 6!";
 

• Here, we simulate rolling a die until we get a 6 using a do-while loop.
• The $roll variable is initialized to 0.
• Inside the loop, we use rand(1, 6) to generate a random number between 1 and 6, simulating a die roll.
• The loop continues until $roll is equal to 6, and it displays each roll along the way.
• Once a 6 is rolled, the loop exits, and it displays "You rolled a 6!"

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$n = 1;
$sum = 0;

do {
    $sum += $n;
    $n++;
} while ($n <= 10);

echo "Sum of numbers from 1 to 10: " . $sum;
 

• In this example, we calculate the sum of numbers from 1 to 10 using a do-while loop.
• We initialize $n to 1 and $sum to 0.
• Inside the loop, we add the current value of $n to $sum and increment $n by 1 in each iteration.
• The loop continues until $n is no longer less than or equal to 10, resulting in the sum of numbers from 1 to 10.

These examples illustrate how PHP do-while loops work and how they can be used for tasks such as user input validation, simulations, and calculations. The key difference from a regular while loop is that the code block is guaranteed to execute at least once.