PHP Exercises: Create a new function that composes multiple functions into a single callable

PHP: Exercise-98 with Solution

Write a PHP program to create a new function that composes multiple functions into a single callable.

Sample Solution:

PHP Code:

<?php
// Licence: https://bit.ly/2CFA5XY

// Function definition for 'compose' that takes a variable number of functions as parameters
function compose(...$functions)
{
    // Use 'array_reduce' to iterate through the functions and create a composition
    return array_reduce(
        $functions,
        function ($carry, $function) {
            // Return a new function that applies the current function to the result of the previous function
            return function ($x) use ($carry, $function) {
                return $function($carry($x));
            };
        },
        // The initial function that simply returns the input
        function ($x) {
            return $x;
        }
    );
}

// Create a composition of two functions: add 2 and multiply by 4
$compose = compose(
    // add 2
    function ($x) {
        return $x + 2;
    },
    // multiply by 4
    function ($x) {
        return $x * 4;
    }
);

// Call the composed function with an argument and display the result using 'print_r'
print_r($compose(2));

// Display a newline
echo("\n");

// Call the composed function with another argument and display the result using 'print_r'
print_r($compose(3));

?>

Sample Output:

16
20

Flowchart:

PHP Code Editor:

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