PHP Functional Programming Passing a callback function as a parameter
Example
There are several PHP functions that accept user-defined callback functions as a parameter, such as: call_user_func(), usort() and array_map().
Depending on where the user-defined callback function was defined there are different ways to pass them:
Procedural style:
function square($number)
{
return $number * $number;
}
$initial_array = [1, 2, 3, 4, 5];
$final_array = array_map('square', $initial_array);
var_dump($final_array); // prints the new array with 1, 4, 9, 16, 25
Object Oriented style:
class SquareHolder
{
function square($number)
{
return $number * $number;
}
}
$squaredHolder = new SquareHolder();
$initial_array = [1, 2, 3, 4, 5];
$final_array = array_map([$squaredHolder, 'square'], $initial_array);
var_dump($final_array); // prints the new array with 1, 4, 9, 16, 25
Object Oriented style using a static method:
class StaticSquareHolder
{
public static function square($number)
{
return $number * $number;
}
}
$initial_array = [1, 2, 3, 4, 5];
$final_array = array_map(['StaticSquareHolder', 'square'], $initial_array);
// or:
$final_array = array_map('StaticSquareHolder::square', $initial_array); // for PHP >= 5.2.3
var_dump($final_array); // prints the new array with 1, 4, 9, 16, 25
