PHP do while Loop
Mastering PHP do-while loop: A Comprehensive Guide with Examples
Introduction:
Explore the power of PHP loops with our in-depth tutorial. Learn about while loops, do-while loops, and the effective use of break and continue statements. Elevate your PHP programming skills with hands-on examples and practical insights.
In PHP, a do-while loop is used to repeatedly execute a block of code as long as a specified condition is true. The key difference between a do-while loop and a while loop is that the do-while loop guarantees that the block of code is executed at least once, even if the condition is initially false.
Here’s the basic syntax of a do-while loop in PHP:
do {
// Code to be executed
} while (condition);The flow of execution is as follows:
The code block inside the do is executed.
The condition is checked after the code block execution.
If the condition is true, the loop continues to iterate, and the code block is executed again.
If the condition is false, the loop exits.
Here’s a simple example to illustrate the do-while loop:
<?php
$counter = 1;
do {
echo "This is iteration number: $counter <br>";
$counter++;
} while ($counter <= 5);
?>In this example, the loop will print the message and increment the $counter variable as long as it is less than or equal to 5.
It’s important to note that the condition is evaluated after the code block is executed, so the code block will always execute at least once, regardless of the initial state of the condition.
A complete example in html with explanation
Here’s a complete example with HTML and PHP, along with explanations for each part:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>PHP do-while Loop Example</title>
</head>
<body>
<h1>PHP do-while Loop Example</h1>
<?php
// Initialize a counter variable
$counter = 1;
// The do-while loop
do {
// Code to be executed inside the loop
echo "This is iteration number: $counter <br>";
// Increment the counter
$counter++;
} while ($counter <= 5);
?>
</body>
</html>Explanation:
<!DOCTYPE html>: Declares the HTML version to be used (HTML5).
<html lang=”en”>: The root HTML element with the language attribute set to English.
<head>: Contains meta-information about the HTML document, such as character set and viewport settings.
<title>: Sets the title of the HTML document, which appears in the browser tab.
<body>: Contains the content of the HTML document that will be displayed in the browser.
The PHP code block inside the <body> element:
<?php … ?>: This is the PHP opening and closing tag.
$counter = 1;: Initializes a counter variable to 1.
do { … } while ($counter <= 5);: The do-while loop. The code inside the do block will be executed at least once, and the loop will continue as long as the condition $counter <= 5 is true.
echo “This is iteration number: $counter <br>”;: Outputs a message with the current value of the counter variable.
$counter++;: Increments the counter variable by 1 in each iteration.
The HTML code outside the PHP block:
<h1>PHP do-while Loop Example</h1>: Adds a heading to the HTML page.
The PHP block outputs messages inside the <body> element.
When you run this PHP script, you’ll see a web page with a heading and messages indicating the iterations of the do-while loop. The loop ensures that the message is displayed at least once
The break Statement
- In PHP, the break statement is used to exit from a loop prematurely, regardless of whether the loop condition is true or false.
- It is commonly used to terminate the execution of a loop when a certain condition is met before the loop’s natural termination.
Here is the basic syntax of the break statement:
<?php
while (condition) {
// Code to be executed
if (/* some condition */) {
break;
}
// More code
}
?>Or within a do-while loop:
<?php
do {
// Code to be executed
if (/* some condition */) {
break;
}
// More code
} while (condition);
?>And within a for loop:
<?php
for ($i = 0; $i < $limit; $i++) {
// Code to be executed
if (/* some condition */) {
break;
}
// More code
}
?>Explanation:
- The break statement causes an immediate exit from the loop, and the program continues with the next statement after the loop.
- It is often used in conjunction with an if statement to check a condition.
- When the condition is met, the break statement is executed, terminating the loop.
The break statement can be used in while, do-while, and for loops.
Here’s a simple example using a while loop:
<?php
$counter = 1;
while ($counter <= 10) {
echo "Current counter value: $counter <br>";
if ($counter === 5) {
echo "Breaking out of the loop at counter = 5 <br>";
break;
}
$counter++;
}
?>In this example, the loop will output messages for the first five iterations, and then it will break out of the loop when the counter reaches 5. The break statement interrupts the loop’s normal flow and exits it immediately.
complete example in html with explanation
Here’s a complete example with HTML and PHP that demonstrates the use of the break statement within a while loop:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>PHP break Statement Example</title>
</head>
<body>
<h1>PHP break Statement Example</h1>
<?php
// Initialize a counter variable
$counter = 1;
// The while loop with a break statement
while ($counter <= 10) {
// Code to be executed inside the loop
echo "Current counter value: $counter <br>";
// Check if the counter is 5
if ($counter === 5) {
echo "Breaking out of the loop at counter = 5 <br>";
// Break out of the loop when counter is 5
break;
}
// Increment the counter
$counter++;
}
?>
</body>
</html>Explanation:
<!DOCTYPE html>: Declares the HTML version to be used (HTML5).
<html lang=”en”>: The root HTML element with the language attribute set to English.
<head>: Contains meta-information about the HTML document, such as character set and viewport settings.
<title>: Sets the title of the HTML document, which appears in the browser tab.
<body>: Contains the content of the HTML document that will be displayed in the browser.
The PHP code block inside the <body> element:
<?php … ?>: This is the PHP opening and closing tag.
$counter = 1;: Initializes a counter variable to 1.
while ($counter <= 10) { … }: The while loop. The code inside the loop will be executed as long as the condition $counter <= 10 is true.
echo “Current counter value: $counter <br>”;: Outputs a message with the current value of the counter variable.
if ($counter === 5) { … }: Checks if the counter is equal to 5.
echo “Breaking out of the loop at counter = 5 <br>”;: Outputs a message indicating that the loop is breaking when the counter is 5.
break;: Breaks out of the loop prematurely
The break Statement with do while loop
Here’s an example that uses the break statement within a do-while loop in PHP, embedded in an HTML page:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>PHP break Statement with do-while Loop Example</title>
</head>
<body>
<h1>PHP break Statement with do-while Loop Example</h1>
<?php
// Initialize a counter variable
$counter = 1;
// The do-while loop with a break statement
do {
// Code to be executed inside the loop
echo "Current counter value: $counter <br>";
// Check if the counter is 3
if ($counter === 3) {
echo "Breaking out of the loop at counter = 3 <br>";
// Break out of the loop when counter is 3
break;
}
// Increment the counter
$counter++;
} while ($counter <= 5);
?>
</body>
</html>Explanation:
<!DOCTYPE html>: Declares the HTML version to be used (HTML5).
<html lang=”en”>: The root HTML element with the language attribute set to English.
<head>: Contains meta-information about the HTML document, such as character set and viewport settings.
<title>: Sets the title of the HTML document, which appears in the browser tab.
<body>: Contains the content of the HTML document that will be displayed in the browser.
The PHP code block inside the <body> element:
<?php … ?>: This is the PHP opening and closing tag.
$counter = 1;: Initializes a counter variable to 1.
do { … } while ($counter <= 5);: The do-while loop. The code inside the loop will be executed at least once, and then the loop will continue as long as the condition $counter <= 5 is true.
`echo “Current counter
The continue Statement with do while loop
- The continue statement is used in PHP to skip the rest of the code inside a loop and move to the next iteration.
- When used in a do-while loop, it causes the program to jump back to the beginning of the loop and reevaluate the loop condition.
Here’s an example demonstrating the continue statement within a do-while loop:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>PHP continue Statement with do-while Loop Example</title>
</head>
<body>
<h1>PHP continue Statement with do-while Loop Example</h1>
<?php
// Initialize a counter variable
$counter = 1;
// The do-while loop with a continue statement
do {
// Check if the counter is even
if ($counter % 2 === 0) {
// Skip the rest of the loop for even numbers
$counter++;
continue;
}
// Code to be executed for odd numbers
echo "Current counter value (odd): $counter <br>";
// Increment the counter
$counter++;
} while ($counter <= 5);
?>
</body>
</html>Explanation:
<!DOCTYPE html>: Declares the HTML version to be used (HTML5).
<html lang=”en”>: The root HTML element with the language attribute set to English.
<head>: Contains meta-information about the HTML document, such as character set and viewport settings.
<title>: Sets the title of the HTML document, which appears in the browser tab.
<body>: Contains the content of the HTML document that will be displayed in the browser.
The PHP code block inside the <body> element:
<?php … ?>: This is the PHP opening and closing tag.
$counter = 1;: Initializes a counter variable to 1.
do { … } while ($counter <= 5);: The do-while loop. The code inside the loop will be executed at least once, and then the loop will continue as long as the condition $counter <= 5 is true.
if ($counter % 2 === 0) { … }: Checks if the counter is even using the modulo operator (%).
continue;: Skips the rest of the loop for even numbers and jumps to the next iteration.
echo “Current counter value (odd): $counter <br>”;: Outputs a message for odd numbers.
$counter++;: Increments the counter variable by 1 in each iteration.
The HTML code outside the PHP block:
<h1>PHP continue Statement with do-while Loop Example</h1>: Adds a heading to the HTML page.
The PHP block outputs messages inside the <body> element.
When you run this PHP script, you’ll see a web page with a heading and messages indicating the iterations of the do-while loop. The loop skips the rest of the code for even numbers and continues with the next iteration.
An application about this lesson with explanation
For simplicity, we’ll create a web application that allows the to input a number and then uses a do-while loop to display a message for each iteration, breaking out of the loop when a specific condition is met, and using the continue statement to skip iterations.
index.php:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>PHP Loop Application</title>
</head>
<body>
<h1>PHP Loop Application</h1>
<form method="post" action="process.php">
<label for="number">Enter a number:</label>
<input type="number" name="number" id="number" required>
<button type="submit">Submit</button>
</form>
</body>
</html>
process.php:
php
<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
// Retrieve the number from the form
$Number = $_POST["number"];
// Validate if the input is a positive integer
if (!is_numeric($Number) || $Number < 1 || floor($Number) != $Number) {
echo "Please enter a valid positive integer.";
} else {
// Initialize a counter variable
$counter = 1;
// The do-while loop with break and continue statements
do {
// Check if the counter is divisible by 3
if ($counter % 3 === 0) {
// Skip this iteration for numbers divisible by 3
$counter++;
continue;
}
// Code to be executed inside the loop
echo "Iteration $counter: ";
// Check if the counter is 5
if ($counter === 5) {
echo "Breaking out of the loop at counter = 5 <br>";
// Break out of the loop when counter is 5
break;
}
// Display a message for the current iteration
echo "Displaying message for counter = $counter <br>";
// Increment the counter
$counter++;
} while ($counter <= $Number);
}
}
?>Explanation:
- index.php contains the HTML form where the can input a number.
- The form sends the data to process.php using the HTTP POST method.
- process.php retrieves the input, validates it, and then uses a do-while loop to display messages for each iteration.
- The loop uses break to exit when the counter reaches 5 and uses continue to skip iterations where the counter is divisible by 3.
- Error handling is included to ensure that the enters a valid positive integer.
You can save these files in the same directory on your web server and access the application through your browser. The index.php file presents the form, and process.php processes the form data and performs the loop logic based on input.
Quiz about PHP loops (while, do-while) and break/continue statements
Here’s a set of 15 quiz questions related to PHP loops (while, do-while) and break/continue statements.Each question is followed by multiple-choice options.
Choose the correct option for each question.
1-What is the purpose of the do-while loop in PHP?
A) To execute a block of code repeatedly while a condition is true.
B) To execute a block of code at least once, then repeat as long as a condition is true.
C) To execute a block of code a specific number of times.
2-Which loop guarantees that the code block will be executed at least once?
A) for loop
B) while loop
C) do-while loop
3-In a while loop, when is the condition checked?
A) Before executing the code block
B) After executing the code block
C) While executing the code block
4-What does the break statement do in a loop?
A) Skips the rest of the loop and moves to the next iteration.
B) Exits the loop prematurely, regardless of the loop condition.
C) Continues to the next iteration of the loop.
5-How is the continue statement different from the break statement?
A) continue exits the loop prematurely; break skips the current iteration.
B) continue skips the rest of the loop and moves to the next iteration; break exits the loop.
C) continue and break are interchangeable.
6-In a do-while loop, when is the condition checked?
A) Before executing the code block
B) After executing the code block
C) While executing the code block
7-Which of the following is true about the do-while loop?
A) It always executes the code block at least once.
B) It never executes the code block.
C) It executes the code block only if the condition is true initially.
8-What is the main purpose of the do-while loop?
A) To repeat a block of code a specific number of times.
B) To execute a block of code repeatedly while a condition is true.
C) To execute a block of code at least once, then repeat as long as a condition is true.
9-Which loop is appropriate when the number of iterations is unknown?
A) for loop
B) while loop
C) do-while loop
10-How is the do-while loop syntax different from the while loop?
A) There is no difference.
B) The condition is placed after the do keyword.
C) The condition is placed before the do keyword.
11-What happens if the break statement is not used in a loop?
A) The loop runs indefinitely.
B) The loop will not execute.
C) The loop continues to the next iteration.
12-In a loop, what does the continue statement do?
A) Exits the loop.
B) Skips the rest of the loop and moves to the next iteration.
C) Repeats the current iteration.
13-Which of the following statements is correct regarding loop control statements in PHP?
A) break and continue can only be used in for loops.
B) break and continue can be used in any type of loop (for, while, do-while).
C) break and continue are not valid in PHP.
14-When using continue in a loop, what happens to the remaining code inside the loop for the current iteration?
A) It is skipped, and the loop continues with the next iteration.
B) It is executed, and the loop continues with the next iteration.
C) The loop terminates.
15-Which loop is suitable when you want to execute a block of code a specific number of times?
A) for loop
B) while loop
C) do-while loop