PHP Custom Exception Class: Creating and throwing custom exceptions

PHP Exception Handling: Exercise-2 with Solution

Write a PHP program that creates a custom exception class in PHP and throw an instance of it within a try block.

Sample Solution:

PHP Code :

<?php
class CustomException extends Exception {
    public function __construct($message, $code = 0, Throwable $previous = null) {
        parent::__construct($message, $code, $previous);
    }
    
    public function __toString() {
        return __CLASS__ . ": [{$this->code}]: {$this->message}\n";
    }
}

try {
    // Code that may throw a custom exception
    $roll_no = -15;
    
    if ($roll_no < 0) {
        throw new CustomException("Roll number cannot be negative.");
    }
    
    echo "Roll number: " . $age;
  } catch (CustomException $e) {
    // Custom exception handling code
    echo "An error occurred: " . $e->getMessage();
}
?>

Sample Output:

An error occurred: Roll number cannot be negative.

Explanation:

In the above exercise,

• In this example, we create a custom exception class CustomException that extends the base Exception class. The custom exception class has a constructor that calls the parent constructor and overrides the __toString() method to provide a custom string representation of the exception.
• Inside the try block, we have a check for a negative age. If the condition is true, we throw an instance of the CustomException class with the message "Age cannot be negative."
• The catch block specifically catches instances of the CustomException class, allowing us to handle the custom exception separately. In this case, we simply display the error message using $e-<getMessage().

Flowchart:

PHP Code Editor:

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