static function substr($str, $start, $end = null)
{
return mb_substr($str, $start, $end == null ? mb_strlen($str, 'UTF-8') : $end, 'UTF-8');
} public function testSubstr()
{
$this->assertEquals('Super', str::substr($this->sample, 0, 5));
$this->assertEquals(' Äwes', str::substr($this->sample, 5, 5));
$this->assertEquals(' Äwesøme String', str::substr($this->sample, 5));
$this->assertEquals('tring', str::substr($this->sample, -5));
}