Ouzo\Utilities\Strings::substringBefore PHP Method

    public static function substringBefore($string, $separator)
    {
        $pos = mb_strpos($string, $separator);
        return $pos !== false ? mb_substr($string, 0, $pos) : $string;
    }

 /**
  * @test
  */
 public function shouldReturnNullForNull()
 {
     //given
     $string = null;
     //when
     $result = Strings::substringBefore(null, ',');
     //then
     $this->assertNull($result);
 }