Invoker.php

functional Invoker.php

<?php

class Invoker {
    
    private $args = [];
    
    function __invoke($a) {
        if (is_callable($a)) {
            $result = array_shift($this->args);
            foreach ($this->args as $arg) {
                $result = $a($result, $arg);
            }
            return $result;
        }
        
        $this->args[] = $a;
        return $this;
    }
}

function calc($a) {
    return (new Invoker())($a);
}

$sum = function($a, $b)  { return $a + $b; };

var_dump(calc(5)(3)(2)($sum));    // 10
var_dump( calc(1)(2)($sum));       // 3
var_dump( calc(2)(3)('pow'));      // 8