PHP Generate coupon Activation code

/** * Generate VIP Activation code * @param int $nums How many coupon codes * @param array $exist _array exclude the coupon code in the specified array * @pa Ram int $code _length The length of the coupon code * @param int $prefix generate the specified prefix * @return array returns excellent Array of Megumi codes*/     Public functionGeneratecode ($nums,$exist _array= ",$code _length= 6,$prefix= ' ' ) {            $characters= "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNPQRSTUVWXYZ"; $promotion _codes=Array();//This array is used to receive the generated coupon code             for($j= 0;$j<$nums;$j++) {                            $code= ' ';  for($i= 0;$i<$code _length;$i++) {                    $code.=$characters[Mt_rand(0,strlen($characters)-1)]; }                            //if the generated 4-bit random number is no longer within the $promotion_codes array we define            if( !In_array($code,$promotion _codes) ) {                    if(Is_array($exist _array) ) {                                            if( !In_array($code,$exist _array) ) {//exclude a coupon code that has been used                            $promotion _codes[$j] =$prefix.$code;//assign the generated new coupon code to the Promotion_codes array                        } Else {                            $j--; }                                        } Else {                                            $promotion _codes[$j] =$prefix.$code;//assign a coupon code to an array                                        }                } Else {                $j--; }        }            return $promotion _codes; }

PHP Generate coupon Activation code