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PHP PHP Functions Function Returns and More PHP Closures

Posted by Colby Work
Colby Work
20,422 Points

Why use "use" and not an argument?

<?php

$name = "Mike";

$greet = function($name) use($name){
  echo "Hello there, $name";
};

$greet();

?>

both result in the same output...

<?php

$greet = function($name){
  echo "Hello there, $name";
};

$greet("Mike");

?>
Stefan Hoffmann
Stefan Hoffmann
24,811 Points

Hello Colby,

i asked a friend of mine some time ago "What do you PHP guys need 'use' for anyway?". Because i personally think its quite ugly. Javascript uses a concept like this to simulate its "classes". But I really didn't expect PHP to have such a thing.

He told me that normally he circumvents this, but there are inversion of control containers for PHP. And the sources of those are full of "use", to construct factories.

Best regards, Stefan

2 Answers

thomascawthorn
thomascawthorn
22,986 Points

In the real world, I've used 'use' for functions like array_filter where you can't define the arguments of the callback. This isn't a great example, but hopefully it gives you a little insight. 

<?php
$flavors = ['vanilla', 'chocolate', 'strawberry', 'raspberry'];

$favorites = ['vanilla', 'chocolate'];

$favoriteFlavors = array_fitler($flavors, function($flavor) use ($favorites) {
    return in_array($flavor, $favorites);
})

$favoriteFlavors // ['vanilla', 'chocolate'];
manav
manav
5,466 Points
manav
manav
5,466 Points

Because 'use' keyword uses the value of variable at the time of closure definition, whereas function argument gets the latest value of variable, no matter what it was at the time of definition.

Change your first example to:

<?php

$name = "Mike";

$greet = function($name) use($name){
  echo "$name";
};

$name = "Tom";

$greet(); // Mike

?>

and change your second example to:

<?php

$greet = function($name){
  echo "$name";
};

$name = "Tom";

$greet($name); // Tom

?>