What is the best way to handle errors and exceptions in DiDOM?

DiDOM is a simple and fast HTML and XML parser written in PHP. When working with DiDOM to scrape web pages or parse XML/HTML content, it's important to properly handle errors and exceptions to ensure the robustness of your application. Here's how you can handle errors and exceptions in DiDOM:

Catching Exceptions

DiDOM can throw exceptions of type DiDom\Exceptions\InvalidSelectorException when you use an invalid CSS selector, and InvalidArgumentException for other invalid arguments. You should catch these exceptions to handle them gracefully.

use DiDom\Document;
use DiDom\Exceptions\InvalidSelectorException;

try {
    $document = new Document('http://example.com');
    $elements = $document->find('invalid:selector');
} catch (InvalidSelectorException $e) {
    // Handle the case where the selector is invalid
    echo 'Invalid CSS selector: ' . $e->getMessage();
} catch (Exception $e) {
    // Handle other general exceptions
    echo 'An error occurred: ' . $e->getMessage();
}

Checking for Empty Results

When using methods like find() to query elements, DiDOM might return an empty array if no elements match the selector. You should check for this condition to prevent further errors in your code:

$elements = $document->find('.some-class');

if (empty($elements)) {
    echo 'No elements found with the class .some-class';
} else {
    // Process the elements
}

Handling Network Errors

If you're loading HTML content from a URL using DiDOM, network errors can occur. DiDOM itself doesn't handle network requests; it processes strings of HTML/XML content. You should use a separate method to retrieve the content, such as cURL or file_get_contents, and handle errors accordingly:

$url = 'http://example.com';
$html = @file_get_contents($url);

if ($html === false) {
    echo 'Failed to retrieve content from ' . $url;
} else {
    $document = new Document($html);
    // Process the document
}

Error Reporting

In PHP, you should also configure error reporting to suit your development or production environment. During development, you may want to enable all error reporting:

error_reporting(E_ALL);
ini_set('display_errors', '1');

In a production environment, you might prefer to log errors instead of displaying them:

ini_set('display_errors', '0');
ini_set('log_errors', '1');
ini_set('error_log', '/path/to/error.log');

Custom Error Handlers

You can also set up a custom error handler to catch and handle PHP warnings and notices that are not exceptions:

set_error_handler(function ($severity, $message, $file, $line) {
    throw new ErrorException($message, 0, $severity, $file, $line);
});

This converts PHP errors into ErrorException objects, which can then be caught using a try-catch block.

DiDOM is quite straightforward in its error handling – most of the error handling work is done by catching exceptions and checking for empty results. When DiDOM does throw an exception, it will be in the form of one of the standard PHP Exception types, so using try-catch blocks is the key to managing these errors. Remember to always validate and sanitize the input and output when working with web scraping to avoid unexpected behavior and potential security risks.