Overloaded functions and function pointers in PHP?

[Peter Salzman]

Hi all,

Since PHP is a (weakly) typed language, is it possible to overload functions
based on the type of their argument?

Also, are there function pointers in PHP?


Here's why I'm asking. Consider these two function:


function foo( $arg ) { echo "foo $arg foo\n"; }

function bar() { echo "barfoo"; }


I'd like to be able to do this:

foo('hello');
foo(&bar());

to produce this:

foo hello foo
foo barfoo foo

Is this at all possible (and convenient!) with PHP?

Thanks!
Pete

[Oli Filth]

Re: Overloaded functions and function pointers in PHP?

Peter Salzman said the following on 10/09/2005 17:21:[color=blue]
> Hi all,
>
> Since PHP is a (weakly) typed language, is it possible to overload functions
> based on the type of their argument?[/color]

No. But there are default arguments, and variable-length argument lists
(PHP 4+).
See http://www.php.net/manual/functions.arguments.php.

[color=blue]
> Also, are there function pointers in PHP?[/color]

No. But there are functions like call_user_func( ), which make them
somewhat redundant.
See http://www.php.net/call_user_func.
[color=blue]
>
> Here's why I'm asking. Consider these two function:
>
>
> function foo( $arg ) { echo "foo $arg foo\n"; }
>
> function bar() { echo "barfoo"; }
>
>
> I'd like to be able to do this:
>
> foo('hello');
> foo(&bar());
>
> to produce this:
>
> foo hello foo
> foo barfoo foo
>[/color]

How about:

function foo($arg)
{
echo "foo $arg foo\n";
}

function bar()
{
return "barfoo";
}

foo(bar());


--
Oli

[Peter Salzman]

Re: Overloaded functions and function pointers in PHP?

Oli Filth <catch@olifilth .co.uk> wrote:[color=blue]
> Peter Salzman said the following on 10/09/2005 17:21:[color=green]
> >
> > Here's why I'm asking. Consider these two function:
> >
> >
> > function foo( $arg ) { echo "foo $arg foo\n"; }
> >
> > function bar() { echo "barfoo"; }
> >
> >
> > I'd like to be able to do this:
> >
> > foo('hello');
> > foo(&bar());
> >
> > to produce this:
> >
> > foo hello foo
> > foo barfoo foo
> >[/color]
>
> How about:
>
> function foo($arg)
> {
> echo "foo $arg foo\n";
> }
>
> function bar()
> {
> return "barfoo";
> }
>
> foo(bar());[/color]


The function argument seems to be executing before the call to foo is made.
In my own code, I'm getting the equivalent of:

barfoo foo foo

rather than

foo barfoo foo


Pete

[Oli Filth]

Re: Overloaded functions and function pointers in PHP?

Peter Salzman said the following on 10/09/2005 17:45:[color=blue]
> Oli Filth <catch@olifilth .co.uk> wrote:
>[color=green]
>>Peter Salzman said the following on 10/09/2005 17:21:
>>[color=darkred]
>>>Here's why I'm asking. Consider these two function:
>>>
>>>
>>> function foo( $arg ) { echo "foo $arg foo\n"; }
>>>
>>> function bar() { echo "barfoo"; }
>>>
>>>
>>>I'd like to be able to do this:
>>>
>>> foo('hello');
>>> foo(&bar());
>>>
>>>to produce this:
>>>
>>> foo hello foo
>>> foo barfoo foo
>>>[/color]
>>
>>How about:
>>
>> function foo($arg)
>> {
>> echo "foo $arg foo\n";
>> }
>>
>> function bar()
>> {
>> return "barfoo";
>> }
>>
>> foo(bar());[/color]
>
>
>
> The function argument seems to be executing before the call to foo is made.
> In my own code, I'm getting the equivalent of:
>
> barfoo foo foo
>
> rather than
>
> foo barfoo foo
>[/color]

That's because your bar() is echoing; mine is returning.

--
Oli

[Chung Leong]

Re: Overloaded functions and function pointers in PHP?

Peter Salzman wrote:[color=blue]
> Since PHP is a (weakly) typed language, is it possible to overload functions
> based on the type of their argument?[/color]

Kind of. You can always check the type of argument that's actually
passed with one of the is_* function and have the function behave
differently (e.g. array vs. scalar).
[color=blue]
> Also, are there function pointers in PHP?[/color]

Kind of. In PHP, functions are referenced by name. If you do $func()
and the variable $func contains the name of a function, it will be
called.
[color=blue]
> I'd like to be able to do this:
>
> foo('hello');
> foo(&bar());
>
> to produce this:
>
> foo hello foo
> foo barfoo foo[/color]

I don't think that's doable in any language.