public function getOrderBy($arg)
    {
        // Check if there are phrases in $arg should handle as it is
        $phrase = explode("\"", $arg);
        if (count($phrase) > 2) {
            // Re-init $arg variable 
            // (It will contain the rest of $arg except phrases).
            $arg = '';
            for ($i = 0; $i < count($phrase); $i++) {
                if ($i % 2 == 0 && $phrase[$i] != '') {
                    // Re-build $arg variable after restricting phrases
                    $arg .= $phrase[$i];
                } elseif ($i % 2 == 1 && $phrase[$i] != '') {
                    // Handle phrases using reqular LIKE matching in MySQL
                    $wordOrder[] = $this->getWordLike($phrase[$i]);
                }
            }
        }
        
        // Handle normal $arg using lex's and regular expresion
        $words = explode(' ', $arg);
        foreach ($words as $word) {
            if ($word != '') {
                $wordOrder[] = 'CASE WHEN ' . 
                               $this->getWordRegExp($word) . 
                               ' THEN 1 ELSE 0 END';
            }
        }
        
        $order = '((' . implode(') + (', $wordOrder) . ')) DESC';
        
        return $order;
    }