Catch SimpleXML Exception only?
SimpleXML throws a regular Exception, how could I differentiate this from other exceptions if the class is the same?
The problem you have is very local and can be easily handled.
Instead of using
$xml = new SimpleXMLElement($buffer);
(the exception-case is that $buffer = '')
You can make use of a function that tells you whether or not loading of the buffer did work w/o throwing an exception:
$xml = simplexml_load_string($buffer);
In case of an error, $xml will be false. So you don't have the exception problem in the first place.
Additionally I suggest you make the code more stable as well if you're interested in more detailed error handling, like checking preconditions and postconditions for the function call:
if (!is_string($buffer) || !strlen($buffer)) {
throw new UnexpectedValueException("String with length required");
}
$xml = simplexml_load_string($buffer);
if (!$xml) {
throw new UnexpectedValueException('String could not be parsed as XML');
}
This also shows how you can throw the exceptions you like. However as you're only concerned about a single line of code you can just catch any exception and deal with the single error-case you have there:
try {
$xml = new SimpleXMLElement($buffer);
} catch (Exception $e) {
$xml = false;
}
But then, using simplexml_load_string might be more handy.
Next to that, you can also enable internal error reporting of libxml and find out more about the actual problems when creating the object:
$saved = libxml_use_internal_errors(true);
$xml = simplexml_load_string($buffer);
$errors = libxml_get_errors();
libxml_use_internal_errors($saved);
if (!$xml) {
var_dump($errors); // create and throw a specific exception here based on errors.
}
However, an empty string won't create any error, better take care if it with a precondition check.
Additionally:
- Make the cron-job save to a different filename while donwloading, replacing the file only when ready.
- Open the file read-only.