Handling 500 Internal Server Error from DomDocument in Laravel 5 - php

Question

The library I wrote for Laravel uses DomDocument.
I use this library under my Controller, and its namespace is app/Services/Verify/. The library gets initialized and used when I put it some inputs into a form.
When the library fails, Laravel would fail the way it would - returning the following message: Whoops, looks like something went wrong.
I use the following regex to validate the URL on the client-side - 'our_team_link' => 'required|url|regex:/^http:\/\/www\.ugcleague\.com\/team_page\.cfm\?clan_id=\d+$/'
Below is my DomXPath code for the above URL.
// Generate our team's HTML file
$this->ourTeamHTML = new \DomDocument;
$this->ourTeamHTML->loadHTMLFile($this->ourTeamURL);
Most of the time the web app works just fine. However, there are cases where even if they type in a URL that is valid by the regex, there are indeed URLs that don't exist (that still get past the regex), and an error like the following gets returned:
PHP Warning: DOMDocument::loadHTMLFile(http://www.ugcleague.com/team_page.cfm?clan_id=8831111118): failed to open stream: HTTP request failed! HTTP/1.1 500 Internal Server Error
in /Users/loop/Code/laravel/app/Services/Verify/ScrapeUGC.php on line 49
Warning: DOMDocument::loadHTMLFile(http://www.ugcleague.com/team_page.cfm?clan_id=8831111118): failed to open stream: HTTP request failed! HTTP/1.1 500 Internal Server Error
in /Users/loop/Code/laravel/app/Services/Verify/ScrapeUGC.php on line 49
Laravel would be linked to the Whoops, looks like something went wrong page.
This confuses the user. I would like to instead return a more descriptive error, that would say, perhaps, "this team does not exist."

Answer 1

You could handle this in Laravel app/Exceptions/Hnadler.php
NB: I have looked in the option of using DOMException handler which is available in PHP, however the error message you are getting in not really and exception by an I/O Warning.
This what PHP native DomException looks like:
/**
* DOM operations raise exceptions under particular circumstances, i.e.,
* when an operation is impossible to perform for logical reasons.
* #link http://php.net/manual/en/class.domexception.php
*/
class DOMException extends Exception {
/**
* #var
* (PHP 5)<br/>
* An integer indicating the type of error generated
* #link http://php.net/manual/en/class.domexception.php#domexception.props.code
*/
public $code;
}
So I came up with this because we can not use DomException to dictate this error since its not an Exception, you can add this in your app/Exceptions/Handler.php
<?php
namespace App\Exceptions;
use Exception;
use Illuminate\Foundation\Exceptions\Handler as ExceptionHandler;
class Handler extends ExceptionHandler
{
/**
* A list of the exception types that should not be reported.
*
* #var array
*/
protected $dontReport = [
\Symfony\Component\HttpKernel\Exception\HttpException::class,
];
/**
* Report or log an exception.
*
* This is a great spot to send exceptions to Sentry, Bugsnag, etc.
*
* #param \Exception $e
* #return void
*/
public function report(Exception $e)
{
return parent::report($e);
}
/**
* Render an exception into an HTTP response.
*
* #param \Illuminate\Http\Request $request
* #param \Exception $e
* #return \Illuminate\Http\Response
*/
public function render($request, Exception $e)
{
$message = $e->getMessage();
if (str_contains($message, 'DOMDocument::loadHTMLFile(): I/O warning')) {
return redirect($request->fullUrl())->with('error', "This team does not exist");
}
//We could also handle DomException like so, but not Dom warning
if ($e instanceof \DomException){
return redirect($request->fullUrl())->with('error', "Your friendly message here");
}
}
}
NB: Be careful when modifying Handler.php, you might start having blank pages instead of Laravel whoops or errors if you don't know what you are doing. You can make a backup somewhere if you are unsure.

Answer 2

There is a php function you will want to use to disable libxml errors.
libxml_use_internal_errors(true);
Now when you are done processing your script, you will need to get any errors generated by using...
$errors = libxml_get_errors();
That would return an array so you can now check it with...
if(count($errors) > 0) {
echo 'This team does not exist';
} else {
echo 'Successful';
}
// Be sure to clear errors
libxml_clear_errors();
You will most likely need to loop through that array and process each error to be sure it's the specific error you are looking for. When working with DOMDocument, you are bound to get a bunch of notices/warnings every time it finds something it doesn't like about invalid HTML/XML.