<?php function generate_code($length = 6) {    $min = pow(10 , ($length - 1));    $max = pow(10, $length) - 1;    return rand($min, $max); }

public static String createRandom(boolean numberFlag, int length){    String retStr = "";    String strTable = numberFlag ? "1234567890" : "1234567890abcdefghijkmnpqrstuvwxyz";    int len = strTable.length();    boolean bDone = true;    do {     retStr = "";     int count = 0;     for (int i = 0; i < length; i++) {      double dblR = Math.random() * len;      int intR = (int) Math.floor(dblR);      char c = strTable.charAt(intR);      if ((‘0‘ <= c) && (c <= ‘9‘)) {       count++;      }      retStr += strTable.charAt(intR);     }     if (count >= 2) {      bDone = false;     }    } while (bDone);      return retStr;   }