Applicatives.php

<?php

function compose($a, $b){
    return function() use ($a, $b){
        $args = func_get_args();
        return $b(call_user_func_array($a, $args));
    };
}

class Just{
    protected $_value;
    
    public function __construct($value){
        $this->set($value);
    }
    
    public function set($value){
        $this->_value = $value;
    }
    
    public function get(){
        return $this->_value;
    }
    
    public function __invoke($func){
        return new Just($func($this->_value));
    }
    
}

interface ApplicativeInterface{
    public function __invoke();
}

class Applicative implements ApplicativeInterface{
    protected $_func;
    public function __construct($func){
        $this->set($func);
    }
    
    public function set($func){
        $this->_func = $func;
    }
    
    public function get(){
        return $this->_func;
    }
    
    public function __invoke(){
        if(func_get_arg(0) instanceof ApplicativeInterface){
            $func = $this->get();
            foreach(func_get_args() as $arg){
                if($arg instanceof ApplicativeInterface){
                    $func = compose($func, $arg->get());
                }
            }
            return new static($func);
        } else {
            return call_user_func_array($this->get(), func_get_args());
        }
    }
}

function aMap($applicative){
    $funcName = __FUNCTION__;
    $params = array_slice(func_get_args(), 1);
    if(is_array($applicative)){
        return array_map(function($actualApplicative) use ($funcName, $params){
            array_unshift($params, $actualApplicative);
            return call_user_func_array($funcName, $params);
        }, $applicative);
    }
    if($applicative instanceof ApplicativeInterface){
        return call_user_func_array($applicative, $params);
    } else {
        throw new Exception('Must be called with Applicative');
    }
}


$plus1Func = function($value){return $value+1;};
$plus3Func = function($value){return $value+3;};
$plus10Func = function($value){return $value+10;};

$pureF1 = new Applicative($plus1Func);
$pureF3 = new Applicative($plus3Func);
$pureF10 = new Applicative($plus10Func);

$result = amap($pureF1, $pureF3, $pureF10);

var_dump($result(1));

var_dump(debug_backtrace());