Filter by Reference

[Swamp56]

I came up with this idea not to long ago when working on the framework I'm developing. I'm just wondering what you guys think of this idea (I'm making it just a function rather than showing the entire filter class):

function filterDeep(&$input) {
     $input = strip_tags(filter_var($input, FILTER_SANITIZE_MAGIC_QUOTES));
}

This allows the programmer to call the method and filter the string entered w/o having to redeclare the variable (seeing as it changes the declaration inside by reference).

$string = "<a href="">username</a>";
filterDeep($string);
echo $string; // outputs 'username'

[NogDog]

It certainly can work. The question is: do you want to restrict yourself whenever you use that function to having it always change the variable you supply it? If you don't pass it by reference and instead return the modified value, then the client code that calls the function can decide in each case what it wants to do.

function filterDeep($var)
{
   return whatever($var);
}

// use whichever way makes sense in each circumstance:
$foo = filterDeep($foo);  // overwrite variable being filtered
$bar = filterDeep($foo);  // assign result to new variable

If instead you use the pass-by-reference technique, in order to accomplish the second case, you'd have to do something like:

$bar = $foo;
filterDeep($bar);

No big deal processing-wise, and in your particular case you may not foresee any need for such a situation, and therefore don't need to worry about it.

[Weedpacket]

My personal preference is to return the return value, rather than using a reference; more generally I like to avoid my functions having side effects because they make the function trickier to analyse (for example, using references make functions more difficult to refactor out because you need to send the reference with it and bring the changed values back again - using pass-by-value semantics means the sending and bringing are built in).

To the extent that I tend to have things like

function sortBy($array, $comparator)
{
    usort($array, $comparator);
    return $array;
}

I just like being able to write

filter(sortBy($foo, $sortfn), $filterfn)

without worrying about side-effects or having pass-by-reference warnings.

[Swamp56]

Thank you for the responses.

The question is: do you want to restrict yourself whenever you use that function to having it always change the variable you supply it?

That's why I have 2 filter classes; one that passes by reference, and one that returns the value ^__ .

[Ashley_Sheridan]

Sounds a bit like re-inventing the wheel you've just made if you're creating two functions for filtering like that. Assuming they are both identical and only differ in the way that things are passed, then you're creating yourself more work should it need to be changed later. I'd just have one function for both purposes. You could get clever and have one function return either a value or change the reference variable depending on a parameter sent to the function, but that's maybe getting a little too involved.

[laserlight]

Ashley Sheridan wrote:

Assuming they are both identical and only differ in the way that things are passed, then you're creating yourself more work should it need to be changed later.

Agreed, although this can be mitigated by having one function be implemented in terms of the other.