When to use ErrorException vs Exception?

Question

PHP 5.1 has introduced ErrorException. The constructor of the two functions differs

public __construct ([ string $message = "" [, int $code = 0 [, Exception $previous = NULL ]]] )
public __construct ([ string $message = "" [, int $code = 0 [, int $severity = 1 [, string $filename = __FILE__ [, int $lineno = __LINE__ [, Exception $previous = NULL ]]]]]] )

Is there a difference when to use either?

I suspect that the above use case is incorrect:

<?php
class Data {
    public function save () {
        try {
            // do something
        } catch (\PDOException $e) {
            if ($e->getCode() == '23000') {
                throw new Data_Exception('Foo Bar', $e);
            }

            throw $e
        }
    }
}

class Data_Exception extends ErrorException /* This should not be using ErrorException */ {}

It isn't documented well, but it appears that ErrorException is designed to be used explicitly from the custom error handler as in the original example, http://php.net/manual/en/class.errorexception.php.

function exception_error_handler($errno, $errstr, $errfile, $errline ) {
    throw new ErrorException($errstr, $errno, 0, $errfile, $errline);
}
set_error_handler("exception_error_handler");

Answer 1

ErrorException is mostly used to convert php error (raised by error_reporting) to Exception.

You should avoid using directly Exception which is too wide. Subclass it with specific Exception or use predefined SPL Exception

To follow your edit : Yes extends Exception rather than ErrorException.