Explain PHP Exceptions

PHP Exceptions are a way to handle errors gracefully in your code. An exception is an object that describes an error or unexpected behavior in a PHP script. When an error occurs, an exception can be thrown, and it can be caught using a try-catch block. This allows you to handle errors in a structured way, making your code more robust and easier to debug.

Here's a basic example to illustrate how exceptions work in PHP:

Basic Example

<?php
function divide($dividend, $divisor) {
    if($divisor == 0) {
        throw new Exception("Division by zero.");
    }
    return $dividend / $divisor;
}

try {
    echo divide(10, 2); // Outputs: 5
    echo divide(10, 0); // Throws an exception
} catch (Exception $e) {
    echo "Caught exception: " . $e->getMessage();
}
?>

Output

5
Caught exception: Division by zero.

Custom Exception Class

You can also create custom exception classes to handle specific types of exceptions.

<?php
class DivideByZeroException extends Exception {}

function divide($dividend, $divisor) {
    if($divisor == 0) {
        throw new DivideByZeroException("Cannot divide by zero.");
    }
    return $dividend / $divisor;
}

try {
    echo divide(10, 2); // Outputs: 5
    echo divide(10, 0); // Throws an exception
} catch (DivideByZeroException $e) {
    echo "Caught DivideByZeroException: " . $e->getMessage();
} catch (Exception $e) {
    echo "Caught general exception: " . $e->getMessage();
}
?>

Output

5
Caught DivideByZeroException: Cannot divide by zero.

Multiple Catch Blocks

You can catch different types of exceptions using multiple catch blocks.

<?php
class DivideByZeroException extends Exception {}
class NegativeNumberException extends Exception {}

function divide($dividend, $divisor) {
    if($divisor == 0) {
        throw new DivideByZeroException("Cannot divide by zero.");
    }
    if($dividend < 0 || $divisor < 0) {
        throw new NegativeNumberException("Negative numbers are not allowed.");
    }
    return $dividend / $divisor;
}

try {
    echo divide(10, 2); // Outputs: 5
    echo divide(10, 0); // Throws DivideByZeroException
    echo divide(-10, 2); // Throws NegativeNumberException
} catch (DivideByZeroException $e) {
    echo "Caught DivideByZeroException: " . $e->getMessage();
} catch (NegativeNumberException $e) {
    echo "Caught NegativeNumberException: " . $e->getMessage();
} catch (Exception $e) {
    echo "Caught general exception: " . $e->getMessage();
}
?>

Output

5
Caught DivideByZeroException: Cannot divide by zero.

Finally Block

You can use a finally block to execute code regardless of whether an exception was thrown or not.

<?php
function divide($dividend, $divisor) {
    if($divisor == 0) {
        throw new Exception("Division by zero.");
    }
    return $dividend / $divisor;
}

try {
    echo divide(10, 2); // Outputs: 5
    echo divide(10, 0); // Throws an exception
} catch (Exception $e) {
    echo "Caught exception: " . $e->getMessage();
} finally {
    echo "This is the finally block.";
}
?>

Output

5
Caught exception: Division by zero.
This is the finally block.

Exceptions in PHP allow you to handle errors more effectively and ensure that your code can handle unexpected situations without crashing.