Custom exception classes in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of custom exception message

What is the output of this PHP code when the exception is thrown and caught?

PHP

<?php
class MyException extends Exception {}

try {
    throw new MyException("Error happened");
} catch (MyException $e) {
    echo $e->getMessage();
}
?>

A No output

B Fatal error

C Error happened

D Exception

💡 Hint

Look at how the exception message is accessed inside the catch block.

The custom exception inherits from Exception and the message passed is 'Error happened'. The catch block prints the message using getMessage(), so the output is exactly that string.

❓ Predict Output

intermediate

Custom exception with additional property

What will be the output of this PHP code?

PHP

<?php
class MyException extends Exception {
    private $codeNumber;
    public function __construct($message, $codeNumber) {
        parent::__construct($message);
        $this->codeNumber = $codeNumber;
    }
    public function getCodeNumber() {
        return $this->codeNumber;
    }
}

try {
    throw new MyException("Error", 404);
} catch (MyException $e) {
    echo $e->getMessage() . ' ' . $e->getCodeNumber();
}
?>

A Error 404

B Error 0

C Error

D Fatal error: Uncaught Error

💡 Hint

Check how the custom property is set and accessed.

The constructor sets the message and the custom codeNumber property. The catch block prints both the message and the codeNumber, so output is 'Error 404'.

❓ Predict Output

advanced

Exception inheritance and catch order

What will be the output of this PHP code?

PHP

<?php
class BaseException extends Exception {}
class ChildException extends BaseException {}

try {
    throw new ChildException("Child error");
} catch (BaseException $e) {
    echo "Caught BaseException: " . $e->getMessage();
} catch (ChildException $e) {
    echo "Caught ChildException: " . $e->getMessage();
}
?>

A No output

B Caught ChildException: Child error

C Fatal error: Uncaught ChildException

D Caught BaseException: Child error

💡 Hint

Remember catch blocks are checked in order and ChildException is a subclass of BaseException.

The first catch block matches because ChildException is a subclass of BaseException. So it catches the exception and prints the message with 'Caught BaseException:'. The second catch block is never reached.

❓ Predict Output

advanced

Custom exception with overridden __toString method

What is the output of this PHP code?

PHP

<?php
class MyException extends Exception {
    public function __toString() {
        return "MyException: " . $this->getMessage();
    }
}

try {
    throw new MyException("Something went wrong");
} catch (MyException $e) {
    echo $e;
}
?>

A MyException: Something went wrong

B Something went wrong

C Fatal error: Object of class MyException could not be converted to string

D Exception: Something went wrong

💡 Hint

Check how the __toString method affects printing the exception object.

The __toString method is overridden to return 'MyException: ' plus the message. When echoing the exception object, this method is called, so the output is 'MyException: Something went wrong'.

🧠 Conceptual

expert

Behavior of uncaught custom exceptions

What happens if a custom exception thrown in PHP is not caught anywhere in the code?

A The exception is ignored and the script continues running normally.

B The script stops and a fatal error message with the exception details is displayed.

C The exception is automatically caught by a default handler and logged silently without stopping the script.

D The exception causes a warning but the script continues execution.

💡 Hint

Think about what happens when an exception is not handled in PHP.

In PHP, if an exception is thrown and not caught, the script stops execution and a fatal error message is shown with the exception details. This helps to avoid silent failures.