设置成员绕过__set的替代方法

Question

The Problem:

In the overload method __set I set members to the same instance. When altering the value to lowercase the method is running twice before the expected behavior is performed.

The Question:

Is there an alternative way to set a member of the instance to prevent the filter and validation process to run twice after altering the key value?

The Code:

class Foo
{
  public function __construct(array $structure = array())
  {
    $this->extend($structure);
  }

  public function extend(array $structure)
  {
    foreach ($structure as $key => $value)
      $this->$key = $value;
  }

  public function __set($name, $value) 
  {
    if(is_array($value) && $this->isAssoc($value))
      $value = new static($value);

    $key = strtolower($name);
    $this->$key = $value;
  }

  protected function isAssoc(array $array) 
  {
    $keys     = array_keys($array);
    $filtered = array_filter($keys, 'is_string');
    $count    = count($filtered);

    return (bool)$count;
  }
}