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Date: Mon, 8 Aug 2005 06:56:43 -0500
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Subject: RE: [PHP-DEV] type hinting throwing a fatal error
From: michaels@crye-leike.com ("Michael Sims")
References: <Pine.LNX.4.62.0508081150140.2940@localhost>

Derick Rethans wrote:
> Hei,
>
> currently if you pass a wrong object's type to a typehinted parameter:
[...]
> 	Fatal error: Argument 1 must be an instance of foo in /tmp/foo.php on
> 	line 3
>
> As type hinting is a new OO thing, it might perhaps make some sense to
> make this an exception instead - as this error might also happen for
> dynamic things by people who use the classes you designed. In that
> case having this fatal error to stop the whole application can be
> annoying. Opinions?

As a PHP user, I have to say I wholeheartedly agree, and I'm glad someone is
raising this issue again.  The last time it was seriously discussed:

http://marc.theaimsgroup.com/?l=php-dev&m=104878782529499&w=2

was less than encouraging.

As a user who is trying to write robust code, my biggest issue is not
whether or not a type hint violation throws an exception, but whether or not
it results in an error than I can trap for.  An exception would be great,
obviously, but I'd be just as happy with an E_WARNING, so at the very least
my custom error handler can catch this.  As you have pointed out, it's
currently a fatal error so a user-defined error handler is not called.

I don't typically comb through my server's php error logs, since I mainly
depend on my custom error handler to let me know when one of my applications
is having problems.  Because of this I have been forced to avoid using type
hints and I've actually implemented by own function to simulate type hints,
like so:

  /* @param SomeObject $foo */
  public function someMethod($foo) {
    checkArgType($foo, 'SomeObject');
  }

checkArgType() throws an exception if $foo isn't instanceof 'SomeObject'.

I would MUCH rather use type hints here.  They're cleaner from a
documentation standpoint and the wtf factor is much lower.  Unfortunately I
can't as long as type hint violations are fatal.

So, I would be very happy if type hint violations either threw and exception
OR triggered an E_WARNING.  As Wez pointed out in
http://marc.theaimsgroup.com/?l=php-dev&m=104911187824684&w=2, currently if
you pass the wrong number of arguments to a function/method you get an
E_WARNING (not a fatal error), so I don't see why type hint violations
shouldn't be treated similarly.  It would increase their value and utility
immensely...