Multiple catch blocks in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of multiple catch blocks with different exceptions

What will be the output of this PHP code with multiple catch blocks?

PHP

<?php
try {
    throw new InvalidArgumentException("Invalid argument!");
} catch (RuntimeException $e) {
    echo "Caught RuntimeException";
} catch (InvalidArgumentException $e) {
    echo "Caught InvalidArgumentException";
} catch (Exception $e) {
    echo "Caught Exception";
}
?>

A Caught RuntimeException

B Caught Exception

C No output, program crashes

D Caught InvalidArgumentException

💡 Hint

The thrown exception matches the first catch block that fits its type.

The thrown exception is InvalidArgumentException. The first catch block for RuntimeException does not match. The second catch block matches exactly, so it runs and prints 'Caught InvalidArgumentException'.

❓ Predict Output

intermediate

Which catch block handles the exception?

Given this PHP code, which catch block will handle the thrown exception?

PHP

<?php
try {
    throw new OutOfRangeException("Out of bounds!");
} catch (InvalidArgumentException $e) {
    echo "Caught InvalidArgumentException";
} catch (OutOfRangeException $e) {
    echo "Caught OutOfRangeException";
} catch (Exception $e) {
    echo "Caught Exception";
}
?>

A Caught OutOfRangeException

B Caught InvalidArgumentException

C Caught Exception

D No output, program crashes

💡 Hint

The exception type matches one of the catch blocks exactly.

The thrown exception is OutOfRangeException. The first catch block is for InvalidArgumentException, which does not match. The second catch block matches exactly, so it runs and prints 'Caught OutOfRangeException'.

❓ Predict Output

advanced

Output when exception matches parent class catch block

What will this PHP code output when an exception is thrown that matches a parent class catch block but not the earlier catch blocks?

PHP

<?php
class MyException extends Exception {}

try {
    throw new MyException("My exception occurred");
} catch (InvalidArgumentException $e) {
    echo "Caught InvalidArgumentException";
} catch (Exception $e) {
    echo "Caught Exception";
} catch (MyException $e) {
    echo "Caught MyException";
}
?>

A Caught Exception

B Caught InvalidArgumentException

C Caught MyException

D No output, program crashes

💡 Hint

Catch blocks are checked in order; parent class catch blocks can catch child exceptions.

The thrown exception is MyException, which extends Exception. The first catch block is for InvalidArgumentException, no match. The second catch block is for Exception, which is a parent class of MyException, so it catches the exception and prints 'Caught Exception'. The third catch block is never reached.

❓ Predict Output

advanced

Output when multiple catch blocks could match

What will this PHP code output when an exception is thrown that matches multiple catch blocks due to inheritance?

PHP

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

try {
    throw new ChildException("Child exception");
} catch (BaseException $e) {
    echo "Caught BaseException";
} catch (Exception $e) {
    echo "Caught Exception";
} catch (ChildException $e) {
    echo "Caught ChildException";
}
?>

A Caught ChildException

B Caught Exception

C Caught BaseException

D No output, program crashes

💡 Hint

Catch blocks are checked in order; the first matching catch block runs.

The thrown exception is ChildException, which extends BaseException. The first catch block is for BaseException, which matches because ChildException is a subclass. So it prints 'Caught BaseException'. The other catch blocks are not reached.

❓ Predict Output

expert

Output when rethrowing exception in multiple catch blocks

What will be the output of this PHP code that rethrows an exception in one catch block and catches it again in another?

PHP

<?php
try {
    try {
        throw new Exception("Original exception");
    } catch (Exception $e) {
        echo "First catch: " . $e->getMessage() . "\n";
        throw $e;
    }
} catch (Exception $e) {
    echo "Second catch: " . $e->getMessage() . "\n";
}
?>

A

First catch: Original exception

B

First catch: Original exception
Second catch: Original exception

C

Second catch: Original exception

D No output, program crashes

💡 Hint

An exception rethrown inside a catch block can be caught by an outer catch block.

The inner try throws an exception caught by the inner catch, which prints 'First catch: Original exception' and rethrows it. The outer catch then catches the rethrown exception and prints 'Second catch: Original exception'.