Map a value to an array of callbacks (reverse of array_map)

Question

Rather than having a single callback walk over the whole array (like array_map), I would like to know if there is a function to have an array of callbacks filter a value.

$value = 'foo';

$closures = array(
    function($value) { return $value . 'bar'; }
    function($value) { return $value . 'baz'; }
);

// Something other than a foreach with call_user_func?
// $value = array_callbacks($closures, $value);

// vs
foreach ($closures as $callback)
{
    $value = call_user_func($callback, $value);
}

print $value; // foobarbaz

newacct · Accepted Answer · 2012-04-06 20:40:24Z

2

What you're describing is called "reduce" or "fold" in functional programming, not "map", since you are trying to process a value through the list of values in order, rather than collecting a list of the results of applying each element to the original value.

The following works:

<?
$value = 'foo';

$closures = array(
    function($value) { return $value . 'bar'; },
    function($value) { return $value . 'baz'; }
);


print array_reduce($closures,
                   function ($value, $callback) { return $callback($value); },
                   $value);
?>

But I agree with the other posters that it might be simpler to use foreach. It is a pain to try to do functional stuff in PHP.

answered Apr 6, 2012 at 20:40

newacct

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Comments

GordonM · Accepted Answer · 2012-04-06 20:17:38Z

2

I think the way you're doing it now is the correct one. As far as I'm aware there's no "reverse array map".

You could create a "wrapper" function around the callbacks that calls each in turn and apply that with array_map, but I don't think you'd get any real benefit from it over the foreach approach.

answered Apr 6, 2012 at 20:17

GordonM

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1 Comment

Tadeck Over a year ago

Foreach is actually clean, simple and does what OP wants. PHP really needs a way to simplify a lot of common tasks, but this task is not one of them. +1

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