array_of realization in php

array_of_example.php

<?php 

class User { 
    public 
        $name, 
        $lastName; 

    public function __construct($name, $lastName) {
        $this->name = $name;
        $this->lastName = $lastName;
    }
}

function array_of ($typename, $input = []) {
    $name = ucfirst(strtolower($typename));
    $containerClassName = 'ArrayOf'.ucfirst(strtolower($typename));
    if (!class_exists($containerClassName)) {
        create_container_class($name);
    }
    return new $containerClassName($input);
}

function create_container_class ($type) {
    eval('class ArrayOf'.$type.' extends ArrayObject {

        public function __construct ($input = [], $flags = 0, $iterator_class = "ArrayIterator") {
            if ($input instanceof '.$type.') $input = [$input];

            if (!is_array($input)) throw new InvalidArgumentException("bad input");

            foreach ($input as $i) if (!($i instanceof '.$type.')) throw new InvalidArgumentException("bad element");

            return parent::__construct($input, $flags, $iterator_class);
        }

        public function offsetSet ($k, $v) {
            if ($v instanceof User) return parent::offsetSet($k, $v);

            throw new InvalidArgumentException("bad user"); 
        }
    }');
}

function names (ArrayOfUser $users) { return array_map(function ($u) { return $u->name; }, $users->getArrayCopy()); }

$arr = array_of ('user');
$arr[] = new User('foo', 'last foo');
$arr[] = new User('bar', 'last bar');

$arr2 = array_of ('user', [
    new User(1,1), 
    new User(2,2)]);