system/Entity.php
public function __isset(string $key): bool
	{
		// Ensure an actual property exists, otherwise
		// we confuse the data mapping.
		$value = property_exists($this, $key) ? $this->$key : null;

		return ! is_null($value);
	}
public function __isset(string $key): bool
	{
		// Ensure an actual property exists, otherwise
		// we confuse the data mapping.
		$value = property_exists($this, $key) ? $this->$key : null;

		return ! is_null($value);
	}
Returns true if a property exists names $key, or a getter method
exists named like for __get().

@param string $key

@return boolean