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($type, $input = []) {
    $class = "ArrayOf$type";
    if (!class_exists($class)) {
        eval("class $class extends ArrayOf {}");
    }
    return new $class($type, $input);
}

abstract class ArrayOf extends ArrayObject {

    private $type;

    public function __construct ($type, $input = [], $flags = 0, $iterator_class = "ArrayIterator") {
        $this->type = $type;
        if (!is_array($input)) $input = [$input];
        foreach ($input as $k => $v) $this->offsetSet($k, $v);
        parent::__construct($input, $flags, $iterator_class);
    }

    public function offsetSet ($k, $v) {
        if ($v instanceof $this->type) return parent::offsetSet($k, $v);
        throw new InvalidArgumentException("Expected $this->type");
    }
}


function test_typehint_function() {
    $arr = array_of ('user');
    $arr[] = new User('foo', 'last foo');
    $arr[] = new User('bar', 'last bar');
    function names (ArrayOfUser $users) { return array_map(function ($u) { return $u->name; }, $users->getArrayCopy()); }
    assert(names($arr) === ['foo', 'bar']);
}

function test_add_array_later() {
    $arr = array_of ('user');
    $arr[] = new User('foo', 'last foo');
    $arr[] = new User('bar', 'last bar');
    foreach ($arr as $v) assert($v instanceof User);
}

function test_add_array() {
    $arr2 = array_of ('user', [
        new User(1,1),
        new User(2,2)]);
    foreach ($arr2 as $v) assert($v instanceof User);
}

function test_add_bad_array() {
    try {
        array_of('user', [new stdclass]);
        assert(false);
    } catch (InvalidArgumentException $e) {
        assert(true);
    }
}

function test_add_one_bad_item() {
    try {
        array_of('user', new stdclass);
        assert(false);
    } catch (InvalidArgumentException $e) {
        assert(true);
    }
}

function test_add_one_item() {
    $arr = array_of('user', new User(1,1));
    assert(count($arr) === 1);
    assert($arr[0] == new User(1,1));
}

function test_typehint_closure() {
    class Foo {};
    $func = function(ArrayOfFoo $a) {};
    $func(array_of('Foo', [new Foo, new Foo]));
    assert(true);
}

function test_typehint_bad_type() {
    $func = function(ArrayOfFoo $a) {};
    try {
        $func(array_of('Foo', [new stdclass, new stdclass]));
        assert(false);
    } catch (InvalidArgumentException $e) {
        assert(true);
    }
}

foreach(preg_grep('#^test#', get_defined_functions()['user']) as $test) {
    echo "$test\n";
    $test();
}