Try-catch execution flow in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to catch exceptions.

PHP

<?php
try {
    // code that may throw an exception
} catch ([1] $e) {
    echo $e->getMessage();
}
?>

Drag options to blanks, or click blank then click option'

AError

BThrowable

CException

DErrorException

Attempts:

3 left

💡 Hint

Common Mistakes

Using a class that does not represent exceptions will cause a fatal error.

Forgetting to specify a class in the catch block.

The Exception class is the base class for all exceptions in PHP and is used in catch blocks to handle exceptions.

2fill in blank

medium

Complete the code to throw an exception.

PHP

<?php
function checkAge($age) {
    if ($age < 18) {
        throw new [1]("Age must be at least 18.");
    }
    return true;
}
?>

Drag options to blanks, or click blank then click option'

AException

BErrorException

CThrowable

DError

Attempts:

3 left

💡 Hint

Common Mistakes

Using a class that is not throwable will cause an error.

Forgetting to use the 'new' keyword when throwing an exception.

The Exception class is used to create and throw exceptions in PHP.

3fill in blank

hard

Fix the error in the catch block to properly catch exceptions.

PHP

<?php
try {
    throw new Exception("Error occurred.");
} catch ([1]) {
    echo "Caught an exception.";
}
?>

Drag options to blanks, or click blank then click option'

AError $e

BException $e

CThrowable $e

DException

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the variable name after the exception class.

Using only the class name without a variable.

The catch block must specify the exception class and a variable to hold the exception object, like Exception $e.

4fill in blank

hard

Fill both blanks to create a try-catch block that catches exceptions and prints the message.

PHP

<?php
try {
    [1] new Exception("Something went wrong.");
} catch ([2] $e) {
    echo $e->getMessage();
}
?>

Drag options to blanks, or click blank then click option'

Athrow

Bcatch

CException

DError

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'catch' instead of 'throw' to raise an exception.

Catching with the wrong class.

Use throw to raise an exception and Exception in the catch block to handle it.

5fill in blank

hard

Fill all three blanks to create a try-catch-finally block that throws an exception, catches it, and executes finally.

PHP

<?php
try {
    [1] new Exception("Failed operation.");
} catch ([2] $e) {
    echo $e->getMessage();
} finally {
    [3] "Cleanup done.";
}
?>

Drag options to blanks, or click blank then click option'

Athrow

BException

Cecho

Dprint

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'print' instead of 'echo' in finally (both work but only one is correct here).

Missing the variable name in catch block.

Use throw to raise the exception, catch with Exception, and print a message with echo in finally.

Practice

1.

What is the main purpose of a try-catch block in PHP?

easy

A. To handle errors without stopping the program

B. To speed up the execution of the program

C. To create new variables automatically

D. To print output to the screen

Solution

1. Step 1: Understand the role of try-catch

   The try block contains code that might cause an error, and the catch block handles that error.

2. Step 2: Identify the purpose

   This structure prevents the program from stopping abruptly by managing errors gracefully.

3. Final Answer:

   To handle errors without stopping the program -> Option A

4. Quick Check:

   Try-catch = error handling [OK]

Hint: Try-catch is for error handling, not speed or output [OK]

Common Mistakes:

• Thinking try-catch speeds up code
• Confusing try-catch with output commands
• Believing try-catch creates variables

2.

Which of the following is the correct syntax to start a try-catch block in PHP?

?

easy

A. try() { /* code */ } catch() { /* handle */ }

B. try: /* code */ catch: /* handle */

C. try { /* code */ } catch (Exception $e) { /* handle */ }

D. try[] { /* code */ } catch[] { /* handle */ }

Solution

1. Step 1: Recall PHP try-catch syntax

   PHP uses curly braces {} to define blocks after try and catch keywords.

2. Step 2: Match correct syntax

   try { /* code */ } catch (Exception $e) { /* handle */ } correctly uses try { } and catch (Exception $e) { } syntax.

3. Final Answer:

   try { /* code */ } catch (Exception $e) { /* handle */ } -> Option C

4. Quick Check:

   Curly braces with try and catch = correct syntax [OK]

Hint: Remember try and catch use curly braces in PHP [OK]

Common Mistakes:

• Using colons instead of braces
• Adding parentheses after try or catch
• Using square brackets instead of braces

3.

What will be the output of this PHP code?

try {
    echo "Start\n";
    throw new Exception("Error happened");
    echo "End\n";
} catch (Exception $e) {
    echo "Caught: " . $e->getMessage() . "\n";
}
echo "Done\n";

medium

A. Start
Caught: Error happened
Done

B. Start
Done

C. Caught: Error happened
Done

D. Start
End
Caught: Error happened
Done

Solution

1. Step 1: Trace code inside try block

   "Start" is printed, then an Exception is thrown, so the next echo "End" is skipped.

2. Step 2: Catch block runs and prints message

   The catch block prints "Caught: Error happened" and then after try-catch, "Done" is printed.

3. Final Answer:

   Start Caught: Error happened Done -> Option A

4. Quick Check:

   Exception stops try, catch prints message, then Done [OK]

Hint: Exception skips rest of try, catch runs, then code continues [OK]

Common Mistakes:

• Thinking code after throw runs
• Missing catch block output
• Assuming program stops after exception

4.

Find the error in this PHP code snippet:

try {
    echo "Hello";
} catch {
    echo "Error caught";
}

medium

A. try block cannot have echo statements

B. Missing exception variable in catch parentheses

C. Missing semicolon after echo statements

D. catch block must come before try block

Solution

1. Step 1: Check catch block syntax

   In PHP, catch must specify the exception type and variable, like catch (Exception $e).

2. Step 2: Identify missing part

   The catch block here has no parentheses or variable, causing a syntax error.

3. Final Answer:

   Missing exception variable in catch parentheses -> Option B

4. Quick Check:

   Catch needs (Exception $e) [OK]

Hint: Catch always needs (Exception $e) or similar [OK]

Common Mistakes:

• Omitting exception variable in catch
• Thinking echo needs semicolon after last statement only
• Believing catch can come before try

5.

Consider this PHP code:

function divide($a, $b) {
    try {
        if ($b == 0) {
            throw new Exception("Division by zero");
        }
        return $a / $b;
    } catch (Exception $e) {
        return $e->getMessage();
    }
}

echo divide(10, 2) . "\n";
echo divide(5, 0) . "\n";

What will be the output?

hard

A. Error
Error

B. 5
0

C. Division by zero
Division by zero

D. 5
Division by zero

Solution

1. Step 1: Analyze divide(10, 2)

   Since 2 is not zero, division happens: 10 / 2 = 5 is returned.

2. Step 2: Analyze divide(5, 0)

   Since 0 triggers exception, catch returns the message "Division by zero".

3. Final Answer:

   5 Division by zero -> Option D

4. Quick Check:

   Valid division returns number; zero divisor returns error message [OK]

Hint: Exception returns message; normal runs return result [OK]

Common Mistakes:

• Expecting zero instead of error message
• Thinking exception stops program without catch
• Confusing return values inside try-catch