如何从特征中的一个函数调用函数（父特征中存在两个函数）

I define traits in php. i was try to communicate between two function witch are present in same traits, I got fatal error.

---------------------------error-------------------------------- Fatal error: Call to undefined function crypto_rand_secure() in /var/www/html/clients/assuredo/include/config/generateToken/token.php on line 28

I was try to call function crypto_rand_secure() in side the function getToken().

trait token
    {
        public function crypto_rand_secure($min, $max)
            {
                $range = $max - $min;
                if ($range < 1) return $min; // not so random...
                $log = ceil(log($range, 2));
                $bytes = (int) ($log / 8) + 1; // length in bytes
                $bits = (int) $log + 1; // length in bits
                $filter = (int) (1 << $bits) - 1; // set all lower bits to 1
                do {
                    $rnd = hexdec(bin2hex(openssl_random_pseudo_bytes($bytes)));
                    $rnd = $rnd & $filter; // discard irrelevant bits
                } while ($rnd > $range);
                return $min + $rnd;
            }

    public function getToken($length)
        {
            $token = "";
            $codeAlphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
            $codeAlphabet.= "abcdefghijklmnopqrstuvwxyz";
            $codeAlphabet.= "0123456789";
            $max = strlen($codeAlphabet); // edited

            for ($i=0; $i < $length; $i++) {
                $token .= $codeAlphabet[crypto_rand_secure(0, $max-1)];
            }

            return $token;
        }
}

As usual in all classes, you have to use $this-> in front of a function name