Anonymous classes in PHP 5.4+

anonclass.php

<?php

function new_($items = null, $extra = "") {
  while (class_exists($name = "Anon".rand(), FALSE)) {};
  $class =
    'class '.$name." ".$extra.PHP_EOL.
    '{'.PHP_EOL.
    '  private $_fns = array();'.PHP_EOL.
    '  public function __construct($items) {'.PHP_EOL.
    '    foreach ($items ?: array() as $name => $value) {'.PHP_EOL.
    '      if (is_callable($value)) {'.PHP_EOL.
    '        $this->_fns[$name] = $value->bindTo($this, $this);'. PHP_EOL.
    '      } else {'.PHP_EOL.
    '        $this->$name = $value;'.PHP_EOL.
    '      }'.PHP_EOL.
    '    }'.PHP_EOL.
    '  }'.PHP_EOL;
  foreach ($items as $key => $value) {
    if (is_callable($value)) {
      $class .= '  public function '.$key.'(';
      $first = true;
      foreach ($params = (new ReflectionFunction($value))->getParameters() as $param) {
        if ($first) { $first = false; } else { $class .= ","; };
        $hint = $param->getClass() ? $param->getClass()->name : "";
        $class .= $hint.' $'.$param->getName();
      };
      $class .= ') { call_user_func_array($this->_fns["'.$key.'"], func_get_args()); }'.PHP_EOL;
    } else {
      $class .= '  public $'.$key.';'.PHP_EOL;
    }
  };
  eval($class."}");
  return new $name($items);
}

interface Test {
  public function setA(DateTime $p);
}
$o = new_([
  'a' => new DateTime("2011-12-19"),
  'setA' => function(DateTime $p) { $this->a = $p; }
], "implements Test");
$o->setA(new DateTime());