Is it possible to pass a function as another function parameter? [duplicate] - php

Question

I need to pass a function as a parameter to another function and then call the passed function from within the function...This is probably easier for me to explain in code..I basically want to do something like this:
function ($functionToBeCalled)
{
call($functionToBeCalled,additional_params);
}
Is there a way to do that.. I am using PHP 4.3.9
Thanks!

Answer 1

I think you are looking for call_user_func.
An example from the PHP Manual:
<?php
function barber($type) {
echo "You wanted a $type haircut, no problem";
}
call_user_func('barber', "mushroom");
call_user_func('barber', "shave");
?>

Answer 2

function foo($function) {
$function(" World");
}
function bar($params) {
echo "Hello".$params;
}
$variable = 'bar';
foo($variable);
Additionally, you can do it this way. See variable functions.

Answer 3

In php this is very simple.
<?php
function here() {
print 'here';
}
function dynamo($name) {
$name();
}
//Will work
dynamo('here');
//Will fail
dynamo('not_here');

Answer 4

I know the original question asked about PHP 4.3, but now it's a few years later and I just wanted to advocate for my preferred way to do this in PHP 5.3 or higher.
PHP 5.3+ now includes support for anonymous functions (closures), so you can use some standard functional programming techniques, as in languages like JavaScript and Ruby (with a few caveats). Rewriting the call_user_func example above in "closure style" would look like this, which I find more elegant:
$barber = function($type) {
echo "You wanted a $type haircut, no problem\n";
};
$barber('mushroom');
$barber('shave');
Obviously, this doesn't buy you much in this example - the power and flexibility comes when you pass these anonymous functions to other functions (as in the original question). So you can do something like:
$barber_cost = function($quantity) {
return $quantity * 15;
};
$candy_shop_cost = function($quantity) {
return $quantity * 4.50; // It's Moonstruck chocolate, ok?
};
function get_cost($cost_fn, $quantity) {
return $cost_fn($quantity);
}
echo '3 haircuts cost $' . get_cost($barber_cost, 3) . "\n";
echo '6 candies cost $' . get_cost($candy_shop_cost, 6) . "\n";
This could be done with call_user_func, of course, but I find this syntax much clearer, especially once namespaces and member variables get involved.
One caveat: I'll be the first to admit I don't know exactly what's going on here, but you can't always call a closure contained in a member or static variable, and possibly in some other cases. But reassigning it to a local variable will allow it to be invoked. So, for example, this will give you an error:
$some_value = \SomeNamespace\SomeClass::$closure($arg1, $arg2);
But this simple workaround fixes the issue:
$the_closure = \SomeNamespace\SomeClass::$closure;
$some_value = $the_closure($arg1, $arg2);

Answer 5

You could also use call_user_func_array(). It allows you to pass an array of parameters as the second parameter so you don't have to know exactly how many variables you're passing.

Answer 6

If you need pass function with parameter as parameter, you can try this:
function foo ($param1){
return $param1;
}
function bar ($foo_function, $foo_param){
echo $foo_function($foo_param);
}
//call function bar
bar('foo', 'Hi there'); //this will print: 'Hi there'
phpfiddle example
Hope it'll be helpful...

Answer 7

If you want to do this inside a PHP Class, take a look at this code:
// Create a sample class
class Sample
{
// Our class displays 2 lists, one for images and one for paragraphs
function __construct( $args ) {
$images = $args['images'];
$items = $args['items'];
?>
<div>
<?php
// Display a list of images
$this->loop( $images, 'image' );
// notice how we pass the name of the function as a string
// Display a list of paragraphs
$this->loop( $items, 'content' );
// notice how we pass the name of the function as a string
?>
</div>
<?php
}
// Reuse the loop
function loop( $items, $type ) {
// if there are items
if ( $items ) {
// iterate through each one
foreach ( $items as $item ) {
// pass the current item to the function
$this->$type( $item );
// becomes $this->image
// becomes $this->content
}
}
}
// Display a single image
function image( $item ) {
?>
<img src="<?php echo $item['url']; ?>">
<?php
}
// Display a single paragraph
function content( $item ) {
?>
<p><?php echo $item; ?></p>
<?php
}
}
// Create 2 sample arrays
$images = array( 'image-1.jpg', 'image-2.jpg', 'image-3.jpg' );
$items = array( 'sample one', 'sample two', 'sample three' );
// Create a sample object to pass my arrays to Sample
$elements = { 'images' => $images, 'items' => $items }
// Create an Instance of Sample and pass the $elements as arguments
new Sample( $elements );