Exception __toString() not working

Hello,

I need to create some custom exceptions.

For example.

<?php

namespace App\Exceptions;

use Exception;

class InvalidMessageException extends Exception
{
    public function __toString()
    {
        return 'General error message : '.$this->message;
    }
}

And to use it I have something like throw new InvalidMessageException($message);.

I'd like to add a general message error from inside the exception et just pass the details ($message) via the exception constructor.

But this doens't work.

Can you help me understand why ?

Thanks a lot.

LaryAI

2 years ago

Level 58

Certainly! The issue you're encountering is related to how PHP handles exceptions and the __toString() method. The __toString() method is not automatically called when an exception is thrown. Instead, it is called when the exception is explicitly converted to a string, such as when you use echo or print on the exception object.

To achieve the behavior you want, you can override the constructor of your custom exception to set a general error message and then append the specific details. Here's how you can do it:

<?php

namespace App\Exceptions;

use Exception;

class InvalidMessageException extends Exception
{
    public function __construct($message = "", $code = 0, Exception $previous = null)
    {
        // Set a general error message and append the specific details
        $generalMessage = 'General error message: ' . $message;
        
        // Call the parent constructor to set the message, code, and previous exception
        parent::__construct($generalMessage, $code, $previous);
    }

    public function __toString()
    {
        return __CLASS__ . ": [{$this->code}]: {$this->message}\n";
    }
}

With this setup, you can throw your custom exception like this:

throw new InvalidMessageException("Specific details about the error.");

When you catch and handle the exception, you can convert it to a string to see the custom message:

try {
    throw new InvalidMessageException("Specific details about the error.");
} catch (InvalidMessageException $e) {
    echo $e; // This will call the __toString() method
}

This will output:

App\Exceptions\InvalidMessageException: [0]: General error message: Specific details about the error.

By overriding the constructor, you ensure that the general error message is always included, and by implementing the __toString() method, you control how the exception is represented as a string.