generateToken.php

<?php

class generateToken {

    public function crypto_rand_secure($min, $max) {
        $range = $max - $min;
        if ($range < 0 ) { return $min; }
        $log = log($range, 2);
        $bytes = (int) ( $log / 8 ) + 1;
        $bits = (int) $log + 1;
        $filter = (int) ( 1 << $bits ) -1;

        do {
            $rnd = hexdec(bin2hex(openssl_random_pseudo_bytes($bytes)));
            $rnd = $rnd & $filter;
        } while ( $rnd >= $range );
        return $min + $rnd;
    }

    public function generateToken($length) {
        $token = '';
        $codeAlphabet = "abcdefghijklmnopqrstuvwxyz";
        $codeAlphabet .= "0123456789";
        for ($i=0; $i < $length; $i++) {
            $token .= $codeAlphabet[$this->crypto_rand_secure(0, strlen($codeAlphabet))];
        }
        return $token;
    }

}