Form Validation in PHP Practice Questions with Solutions

By /

Introduction

Form validation in PHP is an important part of PHP development. It helps ensure that users submit correct and complete information before processing a form. In this chapter, you will learn how to validate names, email addresses, phone numbers, passwords, numbers, and other form data using practical PHP examples.

Question 1: Check Whether a Form Field Is Empty

Problem Statement

Create a PHP program that checks whether a student’s name has been entered. Display an error message if the name is empty.

PHP Solution

<?php

$name = "Rahul";

if (trim($name) === "") {
    echo "Student name is required.";
} else {
    echo "Student Name: " . htmlspecialchars($name);
}

?>

Sample Output

Student Name: Rahul

Try changing $name to an empty string.

$name = "";

Output:

Student name is required.

Explanation

  • trim() removes spaces from the beginning and end of a string.
  • The condition checks whether the name is empty after removing spaces.
  • htmlspecialchars() safely displays the submitted name.

Concepts Covered

  • Empty field validation
  • trim()
  • Conditional statements
  • Safe output

Question 2: Validate an Email Address

Problem Statement

Create a PHP program that checks whether an email address has a valid format.

PHP Solution

<?php

$email = "rahul@gmail.com";

if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo "Valid Email Address";
} else {
    echo "Invalid Email Address";
}

?>

Sample Output

Valid Email Address

Try changing the email:

$email = "rahulgmail.com";

Output:

Invalid Email Address

Explanation

  • filter_var() checks whether a value matches a specified filter.
  • FILTER_VALIDATE_EMAIL checks the email address format.
  • PHP displays a different message depending on the validation result.

Concepts Covered

  • Email validation
  • filter_var()
  • FILTER_VALIDATE_EMAIL
  • If-Else statements

Question 3: Validate a 10-Digit Mobile Number

Problem Statement

Create a PHP program that checks whether a mobile number contains exactly 10 digits.

PHP Solution

<?php

$mobile = "9876543210";

if (preg_match("/^[0-9]{10}$/", $mobile)) {
    echo "Valid Mobile Number";
} else {
    echo "Invalid Mobile Number";
}

?>

Sample Output

Valid Mobile Number

Try changing the mobile number:

$mobile = "98765432";

Output:

Invalid Mobile Number

Explanation

The preg_match() function checks whether a string matches a regular expression.

  • ^ represents the beginning of the string.
  • [0-9] allows digits from 0 to 9.
  • {10} requires exactly 10 digits.
  • $ represents the end of the string.

Concepts Covered

  • Mobile number validation
  • preg_match()
  • Regular expressions
  • Digit checking

Question 4: Validate Age Within a Given Range

Problem Statement

Create a PHP program that checks whether a person’s age is between 18 and 60.

PHP Solution

<?php

$age = 25;

if (!is_numeric($age)) {
    echo "Please enter a valid age.";
} elseif ($age >= 18 && $age <= 60) {
    echo "Age is valid.";
} else {
    echo "Age must be between 18 and 60.";
}

?>

Sample Output

Age is valid.

Try changing the age to 15.

Output:

Age must be between 18 and 60.

Explanation

  • is_numeric() checks whether the value is numeric.
  • && requires both conditions to be true.
  • The age must be at least 18 and no more than 60.

Concepts Covered

  • Numeric validation
  • Range validation
  • is_numeric()
  • Logical AND operator

Question 5: Validate a Password Length

Problem Statement

Create a PHP program that checks whether a password contains at least 8 characters.

PHP Solution

<?php

$password = "Rahul@123";

if (strlen($password) >= 8) {
    echo "Password length is valid.";
} else {
    echo "Password must contain at least 8 characters.";
}

?>

Sample Output

Password length is valid.

Try changing the password:

$password = "abc123";

Output:

Password must contain at least 8 characters.

Explanation

  • strlen() returns the length of a string in bytes.
  • The condition checks whether the password has at least 8 characters for ordinary English letters and numbers.
  • Short passwords are rejected.

Concepts Covered

  • Password validation
  • strlen()
  • Minimum length checking
  • Conditional statements

Question 6: Validate a Password Using Multiple Conditions

Problem Statement

Create a PHP program that checks whether a password contains:

  • At least 8 characters.
  • At least one uppercase letter.
  • At least one lowercase letter.
  • At least one digit.

PHP Solution

<?php

$password = "Rahul123";

if (
    strlen($password) >= 8 &&
    preg_match("/[A-Z]/", $password) &&
    preg_match("/[a-z]/", $password) &&
    preg_match("/[0-9]/", $password)
) {
    echo "Password is valid.";
} else {
    echo "Password does not meet the requirements.";
}

?>

Sample Output

Password is valid.

Explanation

  • strlen() checks the minimum length.
  • [A-Z] checks for an uppercase letter.
  • [a-z] checks for a lowercase letter.
  • [0-9] checks for a digit.
  • && ensures that all conditions must be satisfied.

Concepts Covered

  • Multiple password conditions
  • Regular expressions
  • preg_match()
  • Password validation

Question 7: Validate a Salary Value

Problem Statement

Create a PHP program that checks whether an employee’s salary is numeric and greater than zero.

PHP Solution

<?php

$salary = "35000";

if (!is_numeric($salary)) {
    echo "Salary must be numeric.";
} elseif ($salary <= 0) {
    echo "Salary must be greater than zero.";
} else {
    echo "Valid Salary: ₹" . number_format((float)$salary, 2);
}

?>

Sample Output

Valid Salary: ₹35,000.00

Try changing the salary to:

$salary = "-5000";

Output:

Salary must be greater than zero.

Explanation

  • is_numeric() checks whether the salary contains a valid numeric value.
  • The second condition rejects zero and negative values.
  • number_format() displays the salary with two decimal places.

Concepts Covered

  • Salary validation
  • Numeric checking
  • Negative value checking
  • Number formatting

Question 8: Validate a Dropdown Selection

Problem Statement

Create a PHP program that checks whether a student has selected an allowed course.

PHP Solution

<?php

$course = "PHP";

$allowedCourses = [
    "PHP",
    "Python",
    "Java",
    "JavaScript"
];

if (in_array($course, $allowedCourses, true)) {
    echo "Selected Course: " . htmlspecialchars($course);
} else {
    echo "Please select a valid course.";
}

?>

Sample Output

Selected Course: PHP

Try changing the course:

$course = "C#";

Output:

Please select a valid course.

Explanation

  • $allowedCourses contains the permitted course names.
  • in_array() checks whether the selected course exists in the array.
  • The third argument true enables strict comparison.

Concepts Covered

  • Dropdown value validation
  • in_array()
  • Allowed values
  • Strict comparison

Question 9: Validate a Website URL

Problem Statement

Create a PHP program that checks whether a website address has a valid URL format.

PHP Solution

<?php

$website = "https://www.example.com";

if (filter_var($website, FILTER_VALIDATE_URL)) {
    echo "Valid Website URL";
} else {
    echo "Invalid Website URL";
}

?>

Sample Output

Valid Website URL

Try changing the URL:

$website = "www.example";

Output:

Invalid Website URL

Explanation

  • filter_var() checks the supplied value.
  • FILTER_VALIDATE_URL validates the URL format.
  • A valid URL generally needs a scheme such as https://.

Concepts Covered

  • URL validation
  • FILTER_VALIDATE_URL
  • filter_var()
  • Input checking

Question 10: Build an Employee Registration Validation System

Problem Statement

Create a PHP program that validates employee registration details, including name, email, mobile number, age, and salary. Display a success message only when all details are valid.

PHP Solution

<?php

$name = "Amit Sharma";
$email = "amit@gmail.com";
$mobile = "9876543210";
$age = "28";
$salary = "45000";

$errors = [];

if (trim($name) === "") {
    $errors[] = "Employee name is required.";
}

if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    $errors[] = "Invalid email address.";
}

if (!preg_match("/^[0-9]{10}$/", $mobile)) {
    $errors[] = "Mobile number must contain 10 digits.";
}

if (!filter_var($age, FILTER_VALIDATE_INT) || $age < 18 || $age > 60) {
    $errors[] = "Age must be between 18 and 60.";
}

if (!is_numeric($salary) || $salary <= 0) {
    $errors[] = "Enter a valid salary.";
}

if (empty($errors)) {

    echo "Employee Registration Successful!<br><br>";

    echo "Name: " . htmlspecialchars($name) . "<br>";
    echo "Email: " . htmlspecialchars($email) . "<br>";
    echo "Mobile: " . htmlspecialchars($mobile) . "<br>";
    echo "Age: " . htmlspecialchars($age) . "<br>";
    echo "Salary: ₹" . number_format((float)$salary, 2);

} else {

    echo "Please correct the following errors:<br>";

    foreach ($errors as $error) {
        echo htmlspecialchars($error) . "<br>";
    }
}

?>

Sample Output

Employee Registration Successful!

Name: Amit Sharma
Email: amit@gmail.com
Mobile: 9876543210
Age: 28
Salary: ₹45,000.00

Explanation

  • The program stores all validation errors in an array.
  • Each employee detail is checked separately.
  • filter_var() validates email and integer age.
  • preg_match() validates the mobile number.
  • empty() checks whether the errors array is empty.
  • The employee details are displayed only when every validation passes.

Concepts Covered

  • Multiple field validation
  • Error handling with arrays
  • Email and mobile validation
  • Age and salary validation
  • foreach() loop
  • Complete validation system

Key Takeaways

  • Form validation checks whether submitted information is correct.
  • trim() helps identify empty text fields.
  • filter_var() validates email addresses and other data.
  • preg_match() checks patterns such as mobile numbers and passwords.
  • strlen() checks string length.
  • is_numeric() checks numeric values.
  • in_array() validates allowed selections.
  • Always validate data on the PHP server, even if browser-side validation is used.
  • Use htmlspecialchars() when displaying user-provided text.
  • Never store plain-text passwords; use secure password hashing.

Frequently Asked Questions (FAQs)

1. What is form validation in PHP?

Form validation is the process of checking submitted data to ensure it is complete and follows the required format before processing it.

2. Why is form validation important?

It helps prevent incorrect, incomplete, or unexpected data from entering an application.

3. How do you check an empty field in PHP?

You can use trim() and compare the result with an empty string.

if (trim($name) === "") {
    echo "Name is required.";
}

4. How do you validate an email in PHP?

Use filter_var() with FILTER_VALIDATE_EMAIL.

5. How do you validate a mobile number in PHP?

You can use preg_match() with a regular expression that checks the required number of digits.

6. What is the difference between client-side and server-side validation?

Client-side validation runs in the browser, while server-side validation runs on the server. PHP is commonly used for server-side validation.

7. Can HTML validation replace PHP validation?

No. HTML validation improves the user experience, but users can bypass it. Always validate important data on the server.

8. What is filter_var() in PHP?

filter_var() is a PHP function used to filter or validate values, such as checking email addresses and integers.

9. What is preg_match() used for?

preg_match() checks whether a string matches a specified regular expression. It is useful for validating phone numbers, passwords, and other patterns.

10. How can we display multiple validation errors in PHP?

Store error messages in an array and use a foreach() loop to display them.

Written by Shubhranshu Shekhar, who has trained 20000+ students in coding.

Related Posts

Scroll to Top