Form handling execution flow in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP form handling code?

Consider this PHP script that processes a form submission. What will it output when the form is submitted with name=John?

PHP

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $name = $_POST['name'] ?? 'Guest';
    echo "Hello, $name!";
} else {
    echo "Please submit the form.";
}
?>

A Undefined index: name

B Hello, John!

C Hello, Guest!

D Please submit the form.

💡 Hint

Check the request method and how the $_POST array is used.

The script checks if the request method is POST. If yes, it reads the 'name' from $_POST. Since the form sends 'name=John', it outputs 'Hello, John!'.

❓ Predict Output

intermediate

What happens if the form is submitted with GET method?

Given this PHP code snippet, what will be the output if the form is submitted using the GET method with name=Alice?

PHP

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    echo "Hello, " . htmlspecialchars($_POST['name']) . "!";
} else {
    echo "Form not submitted via POST.";
}
?>

A Form not submitted via POST.

B Hello, Alice!

C Undefined index: name

D Hello, !

💡 Hint

Look at the condition checking the request method.

The code only processes the form if the request method is POST. Since the form uses GET, it skips the POST block and outputs 'Form not submitted via POST.'

🔧 Debug

advanced

Why does this PHP form handler show an error when no input is given?

Examine this PHP code snippet. When the form is submitted without the 'email' field, it shows an error. What causes this error?

PHP

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $email = $_POST['email'];
    echo "Email: $email";
}
?>

A The variable $email is not declared before use.

B The form method is incorrect, it should be GET.

C The echo statement syntax is invalid.

D Accessing <code>$_POST['email']</code> without checking if it exists causes an undefined index error.

💡 Hint

Think about what happens if a key is missing in the $_POST array.

If the form is submitted without the 'email' field, $_POST['email'] does not exist. Accessing it directly causes a PHP notice 'Undefined index'.

📝 Syntax

advanced

Identify the syntax error in this PHP form processing code

What is the syntax error in this PHP snippet that handles form data?

PHP

<?php
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $username = $_POST['username'];
    echo "User: $username";
} else {
    echo "No data received."
}
?>

A Using single quotes instead of double quotes in echo.

B Incorrect comparison operator in the if condition.

C Missing semicolon after the echo statement in the else block.

D Variable $username is not initialized.

💡 Hint

Check the end of each statement carefully.

The else block's echo statement lacks a semicolon at the end, causing a syntax error.

🚀 Application

expert

How many items are in the $_POST array after submitting this form?

Given this HTML form and PHP script, how many key-value pairs will $_POST contain after submission?

HTML form:

<form method="POST" action="submit.php">
  <input type="text" name="first_name" value="Anna" />
  <input type="text" name="last_name" value="Smith" />
  <input type="checkbox" name="subscribe" value="yes" checked />
  <input type="checkbox" name="subscribe" value="no" />
  <input type="submit" value="Send" />
</form>

PHP snippet (submit.php):

<?php
print_r($_POST);
?>

A 3

B 2

C 1

D 4

💡 Hint

Remember how checkboxes with the same name behave in form submission.

Only the checked checkbox with name 'subscribe' and value 'yes' is sent. The form sends 'first_name', 'last_name', and one 'subscribe' value, so $_POST has 3 keys: 'first_name', 'last_name', 'subscribe'. Correct answer: B.