Common validation patterns in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code validating an email?

Consider the following PHP code that checks if an email is valid using filter_var. What will it output?

PHP

<?php
$email = '[e-mail]';
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo 'Valid email';
} else {
    echo 'Invalid email';
}
?>

A Valid email

B Invalid email

C Syntax error

D No output

💡 Hint

filter_var with FILTER_VALIDATE_EMAIL returns the email if valid, false otherwise.

The email '[e-mail]' is a valid email format, so filter_var returns the email string, making the if condition true and printing 'Valid email'.

❓ Predict Output

intermediate

What does this PHP code output when validating a numeric string?

Given this PHP snippet that uses ctype_digit to check if a string contains only digits, what will it output?

PHP

<?php
$input = '12345';
if (ctype_digit($input)) {
    echo 'All digits';
} else {
    echo 'Not all digits';
}
?>

A All digits

B Not all digits

C Warning: ctype_digit expects string

D No output

💡 Hint

ctype_digit returns true if all characters are digits.

The string '12345' contains only digits, so ctype_digit returns true and the code prints 'All digits'.

🔧 Debug

advanced

What error does this PHP code raise when validating a URL?

Examine this PHP code that attempts to validate a URL. What error or output will it produce?

PHP

<?php
$url = 'http://example.com';
if (filter_var($url, FILTER_VALIDATE_URL)) {
    echo 'Valid URL';
} else {
    echo 'Invalid URL';
}
?>

A Warning: filter_var expects parameter 2 to be int

B Invalid URL

C Valid URL

D Syntax error

💡 Hint

FILTER_VALIDATE_URL checks if the string is a valid URL format.

The string 'http://example.com' is a valid URL, so filter_var returns the URL string, making the if condition true and printing 'Valid URL'.

❓ Predict Output

advanced

What is the output of this PHP code validating a password length?

This PHP code checks if a password length is at least 8 characters. What will it output?

PHP

<?php
$password = 'pass123';
if (strlen($password) >= 8) {
    echo 'Password is strong';
} else {
    echo 'Password too short';
}
?>

A No output

B Password is strong

C Warning: strlen expects parameter 1 to be string

D Password too short

💡 Hint

strlen returns the length of the string.

The password 'pass123' has 7 characters, which is less than 8, so the code prints 'Password too short'.

🧠 Conceptual

expert

Which option correctly describes the behavior of PHP's filter_var with FILTER_VALIDATE_INT and options?

Consider the following PHP code snippet:

$options = ['options' => ['min_range' => 1, 'max_range' => 10]];
$value = 5;
$result = filter_var($value, FILTER_VALIDATE_INT, $options);

What does $result contain after execution?

A The string '5' because filter_var always returns strings

B The integer 5 because it is within the range 1 to 10

C Null because the options array is ignored

D Boolean false because filter_var does not accept options with FILTER_VALIDATE_INT

💡 Hint

FILTER_VALIDATE_INT accepts an options array to specify min and max range.

filter_var returns the integer value if it is within the specified range. Since 5 is between 1 and 10, $result is 5 (int).