Object Instance-time Trait Application.

TraitExt.php

<?php
use Symfony\Component\ClassLoader\UniversalClassLoader;

class TraitExt {
  public static $clsLoader;
  
  public static function withTraits($class, array $traits) {
    $cache = self::classLoader()->getNamespaceFallbacks();
    if (empty($cache)) {
      self::registerCacheDir($_SERVER["TMPDIR"] . DIRECTORY_SEPARATOR . "trait_ext_cache");
    }
    
    if (! class_exists($class, true)) {
      // 例外を投げる
      throw new InvalidArgumentException("未定義クラス({$class})");
    }
    
    $refClass = new ReflectionClass($class);
    
    if (empty($traits)) return new TraitExtActivator($refClass);
    
    // traitsの確認
    $without = array_diff($traits, $refClass->getTraitNames());
    if (empty($without)) {
      return new TraitExtActivator($refClass);
    }
    
    // クラス名の決定
    $traitWithclass = $class . implode("", array_map(
      function ($v) {
        if (false !== ($p = strrpos($v, '\\'))) $v = substr($v, $p+1);
        
        return $v;
      },
      $without
    ));
    
    // キャッシュからの探索
    if (self::classLoader()->findFile($traitWithclass) === null) {
      // trait拡張クラスをエクスポートする
      self::export($traitWithclass, $class, $without);
    }
    
    return new TraitExtActivator(new ReflectionClass($traitWithclass));
  }
  
  public static function classLoader(UniversalClassLoader $loaderClass = null) {
    if (self::$clsLoader === null) {
      if ($loaderClass !== null) {
        self::$clsLoader = new $loaderClass();
      }
      else {
        self::$clsLoader = new UniversalClassLoader();
      }
      self::$clsLoader->register();
    }
    
    return self::$clsLoader;
  }
  
  public static function registerCacheDir($dir) {
    self::classLoader()->registerNamespaceFallbacks(array($dir));
    self::classLoader()->registerPrefixFallbacks(array($dir));
  }
  
  private static function export($className, $parentClass, array $traits) {
    if (preg_match('/(?:\\\\)?(.*)\\\\(.+)/', $className, $m) === 1) {
      array_shift($m);
      if (count($m) === 1) {
        $namespace = "";
        $shortClass = $m[0];
      }
      else {
        list($namespace, $shortClass) = $m;
      }
    }
    
    $ns = $namespace !== "" ? "namespace {$namespace}" : "";
    $tr = implode(",", $traits);
    
    $code = <<< WITH_TRAITS
<?php
  {$ns};
  class {$shortClass} extends {$parentClass} {
    use {$tr};
  }
WITH_TRAITS;
    
    $dir = sprintf("%s%s%s", 
      implode("", self::classLoader()->getNamespaceFallbacks()), DIRECTORY_SEPARATOR,
      str_replace('\\', DIRECTORY_SEPARATOR, $namespace)
    );
    $filename = $dir . DIRECTORY_SEPARATOR . sprintf("%s.php", $shortClass);
    
    if (! file_exists($dir)) {
      mkdir($dir, 0777, true);
    }
    
    file_put_contents($filename, $code);
  }
}

class TraitExtActivator {
  private $className;
  
  public function __construct(ReflectionClass $classRef) {
    $this->classRef = $classRef;
  }
  
  public function newInstance() {
    $args = func_get_args();
    if (empty($args)) {
      return $this->classRef->newInstanceArgs();
    }
    else {
      return $this->classRef->newInstanceArgs($args);
    }
  }
  
  public function getClassName() {
    return sprintf('\%s', $this->classRef->getName());
  }
}

TraitExtTestDriver.php

<?php
namespace My;

require_once __DIR__ . "/../lib/Symfony/Component/ClassLoader/UniversalClassLoader.php";
require_once __DIR__ . "/TraitExt.php";

define ("CACHE_DIR", __DIR__ . "/cache");

\TraitExt::registerCacheDir(CACHE_DIR);

class Animal {
  public function getKind() {
    return "UMA";   
  }
    
    // メソッドの宣言
    public function cry() {
        return "．．．";
    }
    
    public function greeting() {
      return sprintf("%s : %s\n", $this->getKind(), $this->cry());
    }
}
$animal = new Animal();
echo $animal->greeting();

trait Cat {
  function getKind() {
    return "ぬこ";
  }
  
  function Cry() {
    return "我が輩は猫であった";
  }
}

$c = \TraitExt::withTraits("\My\Animal", ["\My\Cat"]);
$animal = $c->newInstance();
echo $animal->greeting();

trait Dog {
  function getKind() {
    return "いぬ";
  }
  
  function Cry() {
    return "今日も平和。わんわんお";
  }
}

$animal = \TraitExt::withTraits($c->getClassName(), ["\My\Dog"])->newInstance();
echo $animal->greeting();