Gravatar.php
public function setDefaultImage($image)
	{
		// Quick check against boolean false.
		if($image === false)
		{
			$this->default_image = false;

			return $this;
		}

		// Wipe out the param cache.
		$this->param_cache = NULL;

		// Check $image against recognized gravatar "defaults", and if it doesn't match any of those we need to see if it is a valid URL.
		$_image = strtolower($image);
		$valid_defaults = array('404' => 1, 'mm' => 1, 'identicon' => 1, 'monsterid' => 1, 'wavatar' => 1, 'retro' => 1);
		if(!isset($valid_defaults[$_image]))
		{
			if(!filter_var($image, FILTER_VALIDATE_URL))
			{
				throw new InvalidArgumentException('The default image specified is not a recognized gravatar "default" and is not a valid URL');
			}
			else
			{
				$this->default_image = rawurlencode($image);
			}
		}
		else
		{
			$this->default_image = $_image;
		}

		return $this;
	}
public function setDefaultImage($image)
	{
		// Quick check against boolean false.
		if($image === false)
		{
			$this->default_image = false;

			return $this;
		}

		// Wipe out the param cache.
		$this->param_cache = NULL;

		// Check $image against recognized gravatar "defaults", and if it doesn't match any of those we need to see if it is a valid URL.
		$_image = strtolower($image);
		$valid_defaults = array('404' => 1, 'mm' => 1, 'identicon' => 1, 'monsterid' => 1, 'wavatar' => 1, 'retro' => 1);
		if(!isset($valid_defaults[$_image]))
		{
			if(!filter_var($image, FILTER_VALIDATE_URL))
			{
				throw new InvalidArgumentException('The default image specified is not a recognized gravatar "default" and is not a valid URL');
			}
			else
			{
				$this->default_image = rawurlencode($image);
			}
		}
		else
		{
			$this->default_image = $_image;
		}

		return $this;
	}
Set the default image to use for avatars.
@param mixed $image - The default image to use. Use boolean false for the gravatar default, a string containing a valid image URL, or a string specifying a recognized gravatar "default".
@return \thomaswelton\GravatarLib\Gravatar - Provides a fluent interface.

@throws \InvalidArgumentException