Why is this function going into infinite loop?

Question

I made this function to return a unique code ( it checks if already exists searching in a webservice), but when run, it is running forever, does not return me result.

public function generateuniquecode(){
    function generatecode(){
      $upper = implode('', range('A', 'Z')); // ABCDEFGHIJKLMNOPQRSTUVWXYZ
      $nums = implode('', range(0, 9)); // 0123456789
      $alphaNumeric = $upper.$nums; // ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789
      $code = '';
      for($i = 0; $i < 6; $i++) {
          $code .= $alphaNumeric[rand(0, strlen($alphaNumeric) - 1)];
      }
      return $code; // ex: X0XX0X
    }
    $exists = false;
    while($exists == false) {
      $code = generatecode();
      $response = $this->seachcardbycode($code);
      if($response['success'] == false){
        if($response['data']['code'] == 1){
          $exists = false;
        }else{
          die('code 0');
          // code 0
          // curl call error
        }
      }else{
        $exists = true;
      }
    }
    return $code; 
  }

The seachcardbycode function returns an array like this:

array(
      "success"=>false / true,
      "data"=>outro array
    );

Answer 1

Apparently the problem is in your code, in the section where starts the IF.

if($response['success'] == false)

To be more precise in the answer would be interesting you post the code of the whole function the seachcardbycode. To see the possibilities of the value of $response['success'] be amended. At first it always comes with the value false thus the Else will never be triggered, and the value of $existes will never be changed.

If it is not passed to $response no object where Success is equal to false, really will stay in an infinite loop this code.