PHP Nested if Statement

Learn PHP and HTML Basics: Web Development Fundamentals

Introduction:

Welcome to our comprehensive guide on PHP and HTML basics! In this lesson, we’ll cover essential concepts in web development, including PHP scripting and HTML markup. Whether you’re a beginner or looking to reinforce your skills, this tutorial will provide a solid foundation for building dynamic and interactive web pages.

In PHP, you can use nested if statements to create more complex conditional logic by placing one if statement inside another. This allows you to check multiple conditions and execute different blocks of code based on the outcomes of these conditions.

Here’s a simple example of a nested if statement:

<?php

$number = 15;

if ($number > 10) {
echo "The number is greater than 10.";

if ($number % 2 == 0) {
echo " Additionally, it is an even number.";
} else {
echo " Additionally, it is an odd number.";
}
} else {
echo "The number is not greater than 10.";
}

?>

In this example, the outer if statement checks if $number is greater than 10. If it is, it enters the block and then further checks whether the number is even or odd using the nested if statement.
The appropriate message is echoed based on the conditions.

You can nest if statements as deeply as needed to accommodate your specific logic requirements, but be mindful of code readability. Excessive nesting can make your code harder to understand, and it might be worth considering alternative approaches like switch statements or refactoring your logic to make it more modular.

complete code example in html with explanation

Let’s create a simple HTML page with a form that takes a ‘s age as input and provides a message based on their age using PHP and nested if statements.

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Age Checker</title>
</head>
<body>

<h1>Age Checker</h1>

<?php
// Check if the form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
// Retrieve the 's age from the form
$Age = $_POST["age"];

// Check the age and display a message
if ($Age >= 18) {
echo "<p>You are an adult.</p>";
} else {
// Nested if statement to check if the age is a valid positive number
if ($Age > 0) {
echo "<p>You are a minor.</p>";
} else {
echo "<p>Please enter a valid age.</p>";
}
}
}
?>

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>">
<label for="age">Enter your age:</label>
<input type="text" id="age" name="age">
<button type="submit">Check Age</button>
</form>

</body>
</html>

Explanation:

HTML Structure:

The HTML document contains a simple form with a text input to enter the age and a submit button.
PHP code is embedded within the HTML to process the form submission and display messages based on the ‘s age.

PHP Code:

if ($_SERVER[“REQUEST_METHOD”] == “POST”): Checks if the form has been submitted using the POST method.
$Age = $_POST[“age”];: Retrieves the ‘s age from the submitted form data.
The nested if statements check the ‘s age:
if ($Age >= 18): If the age is 18 or above, it prints a message indicating that the is an adult.
else: If the age is below 18, it further checks:
if ($Age > 0): If the age is a valid positive number, it prints a message indicating that the is a minor.
else: If the age is not a valid positive number, it prints a message asking the to enter a valid age.
Form Action:

action=”<?php echo htmlspecialchars($_SERVER[“PHP_SELF”]); ?>”: The form is submitted to the same PHP script (the current page).

This is a simple example to demonstrate the usage of nested if statements in PHP within an HTML context. Depending on your requirements, you may need to add more validation or create a more sophisticated structure.

An application to check if a is eligible to vote

let’s create a simple web application that uses PHP and HTML to check if a is eligible to vote based on their age.
We’ll create a form where s can enter their age, and the application will display a message indicating whether they are eligible to vote or not.

index.php:

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Voting Eligibility Checker</title>
</head>
<body>

<h1>Voting Eligibility Checker</h1>

<?php
// Check if the form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
// Retrieve the 's age from the form
$Age = $_POST["age"];

// Check the age and display a message
if ($Age >= 18) {
$message = "You are eligible to vote!";
} else {
// Nested if statement to check if the age is a valid positive number
if ($Age > 0) {
$message = "You are not eligible to vote. You must be at least 18 years old.";
} else {
$message = "Please enter a valid age.";
}
}
}
?>

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>">
<label for="age">Enter your age:</label>
<input type="text" id="age" name="age" required>
<button type="submit">Check Eligibility</button>
</form>

<?php
// Display the eligibility message if it exists
if (isset($message)) {
echo "<p>$message</p>";
}
?>

</body>
</html>

Explanation:

HTML Structure:

The HTML document contains a form with a text input for entering the age and a submit button.
PHP code is embedded within the HTML to process the form submission and display messages based on the ‘s age.

PHP Code:

If the form is submitted, it retrieves the ‘s age from the form and checks whether the is eligible to vote.
The eligibility message is stored in the $message variable.
The form action is set to the current PHP script (htmlspecialchars($_SERVER[“PHP_SELF”])).

Form Validation:

The <input> tag has the required attribute, ensuring that the must enter their age before submitting the form.

Displaying Message:

After processing the form, if the $message variable is set, it is displayed to the .
This simple application demonstrates how to create a basic form using HTML and process the form data using PHP with nested if statements to check eligibility. Depending on your needs, you can enhance and extend this application with additional features and validations.

Quiz about this lesson:15 questions

Here’s a quiz with 15 questions related to PHP and HTML, particularly focusing on the concepts discussed in the previous examples.

Each question has multiple-choice answers, and the correct answers are indicated.

Quiz: PHP and HTML Basics

1-What does PHP stand for?

A) Personal Home Page
B) Preprocessed Hypertext Processor
C) Public Hosting Platform
D) Personal Hypertext Preprocessor
Correct Answer: D

2-Which HTML tag is used to define the structure of an HTML document?

A) <head>
B) <body>
C) <html>
D) <title>
Correct Answer: C

3-In PHP, how do you check if a variable is set?

A) isset()
B) is_set()
C) check_var()
D) var_exists()
Correct Answer: A

4-What is the purpose of the htmlspecialchars function in PHP?

A) Convert special characters to HTML entities
B) Create hyperlinks in HTML
C) Check if a variable is numeric
D) Validate email addresses
Correct Answer: A

5-Which method is commonly used to process form data in PHP?

A) GET
B) POST
C) REQUEST
D) FORM
Correct Answer: B

6-What is the purpose of the required attribute in an HTML form input?

A) Force the browser to submit the form
B) Indicate that the input is optional
C) Validate the input using JavaScript
D) Specify that the input must be filled out
Correct Answer: D

7-Which PHP function is used to retrieve form data sent with both GET and POST methods?

A) get_data()
B) read_form()
C) form_data()
D) $_REQUEST[]
Correct Answer: D

8-In PHP, what does the $_SERVER[“PHP_SELF”] variable represent?

A) The server’s IP address
B) The current script’s filename
C) The PHP version installed
D) The server’s operating system
Correct Answer: B

9-What is the purpose of the <meta charset=”UTF-8″> tag in an HTML document?

A) Define the document’s character set
B) Create a meta description for search engines
C) Specify the document’s language
D) Link to an external stylesheet
Correct Answer: A

10-Which PHP conditional statement is used for multiple alternative conditions?

A) if
B) switch
C) elseif
D) case
Correct Answer: C

11-What does the htmlspecialchars function help prevent in PHP?

A) SQL injection attacks
B) Cross-site scripting (XSS) attacks
C) Session hijacking
D) Cross-site request forgery (CSRF)
Correct Answer: B

12-Which HTML tag is used to create a hyperlink?

A) <a>
B) <link>
C) <href>
D) <hyperlink>
Correct Answer: A

13-What is the purpose of the echo statement in PHP?

A) Redirect the to another page
B) Output content to the browser
C) Execute a loop
D) Include an external file
Correct Answer: B

14-Which PHP function is used to validate email addresses?

A) validate_email()
B) filter_var()
C) check_email()
D) verify_email()
Correct Answer: B

15-In HTML, what does the <form> tag define?

A) A table
B) A section of text
C) A form for input
D) A horizontal rule
Correct Answer: C

PHP Tutorial

Curriculum