处理来自外部库的错误（simple_html_dom）

Question

I'm building a page to crawl some web pages.

It works, usually, but everyone once in a while, it will fail to grab the page, and throw the following error:

( ! ) Warning: file_get_contents(URLWASHERE): failed to open stream: HTTP request failed! HTTP/1.1 404 Not Found in Z:\Wamp\www\spider\simple_html_dom.php on line 555

Here is how I'm grabbing the page:

$page->load_file('URLWASHERE');

---

Is there a way to figure out if that error happens? I don't know how to detect it because it's in the library, not my code.

I can't use if (!$page) because it still returns something. But that something doesn't seem very helpful, though it is significantly shorter.

---

You can see output here:

$page when successful: http://pastebin.com/CnRVP6SK

$page when failed: http://pastebin.com/t9q6Gwnf

---

I just want to be able to find out if there was an error so I can have my program try again.

Answer 1

You can use the error_get_last() function to get info about the last error. You might also consider silencing the warning message with the @ operator.

@file_get_contents('http://example.com/wjqlshqwd');

$error = error_get_last();
if($error && strpos($error['message'], '404') !== false)
{
    echo 'There was an error';
}

Also before running this code you should reset the state of error_get_last(), a comment on the PHP manual page describes a trick to do that:

// var_dump or anything else, as this will never be called because of the 0
set_error_handler('var_dump', 0);
@$undef_var;
restore_error_handler();

// error_get_last() is now in a well known state:
// Undefined variable: undef_var

The concept is just to create a known error.