recursive function in php class

Question

I want to create a function in class, to create username, function will check if username exist then it will increment username like username_1. and check if this username exist or not if it exist again increment it to username_2 till new username created. I have created this function but it return me nothing.Please help me what is wrong in my code.

class a{

function check_username($username){


  if($usernameexist){

    return true;
  }
  else
  {

   return false;

  }

}

function create_username($username) {

        $__name = __FUNCTION__;

        if ($this->check_username($username)) {                
            $n++;
            $username = $username . "_" . $n;
            //return $__name($username);  this return fatal error.
            return call_user_func('create_username', $username);

        } else {
            return $username;               
        }
    }
}

@Nanne I'd prefer var_dump(), if something... Echo is used for non-debugging purposes too, and it is a lot more easy to "turn on and off" var_dump statements using plain text replace in any decent text editor than to do the same with echo statements only for debugging purposes.... — ppeterka
– ppeterka, Commented Jan 16, 2013 at 13:35
True, but I don't think that really matters in this minimal case. And seeing the amount of debugging work allready done, I don't think the OP needs to be confused with discussion about that :) — Nanne
– Nanne, Commented Jan 16, 2013 at 13:36
@Nanne I understand your motivation, but I'm more a fan of "do it right from the beginning" - especially with var_dump. I had too many problems coming from not using var_dump, I literally wasted days from my life not doing so. That's why I always mention it whenever the subject comes up - might save the days I lost for some people... — ppeterka
– ppeterka, Commented Jan 17, 2013 at 8:38

Brad Christie · Accepted Answer · 2013-01-16 13:53:48Z

3

No need to use recursion for this, a simple while(){} loop will do:

Plain-Jane Interator method

// your original function
function create_username($username){
  // check if the username (as-is) already exists
  if ($this->check_username($username)){
    // use $n to keep a counter
    $n = 1;
    // while {username}_{n} exists, keep incrementing the counter
    while ($this->check_username($username.'_'.$n)){
      $n++;

      /* If you don't want this to check to infinity, uncomment
       * the below portion. the 100 is an arbitrary number, but use
       * whatever you want as a limitation (could even make it a
       * parameter in the method). Also, returning FALSE allows you to
       * gracefully catch when max attempts are reached.
       *
       * e.g.
       *   if (($new_user = $obj->create_username('BradChristie')) !== FALSE){
       *     // user was successfully created within the max allowed attempts
       *   }
       */
      //if ($n > 100) return FALSE
    }
    // return the result
    return $username.'_'.$n;
  }
  // username was fine, return it back
  return $username;
}

Recursive method

// recursive username check
public function create_username($username, $n = 0)
{
  /* Same as above function, this is a check to prevent counting
   * to infinity. uncomment to apply it
   */
  //if ($n > 100) return FALSE;

  // establish the username we're testing. if $n is 0,
  // it's the original call to the function (don't add _0)
  // if it's >0, it's part of the search so include it
  $_username = $username . ($n > 0 ? '_'.$n : '');

  // check if the username exists.
  if ($this->check_username($_username))
  {
    // it exists, so make a call to this same function passing
    // the original username and the value of n + 1 (move to next
    // possibility)
    return $this->create_username($username, $n+1);
  }

  // the name, as-is, was fine. return it
  return $_username;
}

Example

edited Jan 16, 2013 at 13:53

answered Jan 16, 2013 at 13:30

Brad Christie

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1 Comment

Coder Web Over a year ago

I have done this by modifying function function create_username($username,$n=0) { $newusername = $this->add_username($username, $n); if(strtolower($this->check_username($newusername)) == 'true'){ $n++; return $this->create_username($username,$n); } else{ return $newusername; } } function add_username($username,$n){ if($n > 0){ $username = $username."_".$n; } return $username; }

borrible · Accepted Answer · 2013-01-16 13:35:20Z

0

Your code is wrong in several ways and, as pointed out elsewhere, your desired function is better written iteratively.

Some of the problems with your code are as follows:

You are doing your recursive check when check_username has succeeded. So, if you fail to find the original $username you are never modifying it, so never checking the modified value.
You are modifying the name passed to create_username by appending _n (for appropriate n). Since you are passing a modified name in your recursive call you will actually end up with multiple _n parts on the name.
Since you are not limiting your recursive calls, even if this was written correctly, you would eventually get nested too deep.

answered Jan 16, 2013 at 13:35

borrible

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Comments

ppeterka · Accepted Answer · 2013-01-16 13:36:29Z

0

There is no need for recursivity in this case... A simple loop would do just perfectly:

function create_username($username) {

    $original_username = $username;
    $i=1;
    while(! $this->check_username($username) ) {
        $username = $original_username . '_' .$i++;
    }

    return $username;
}

edited Jan 16, 2013 at 13:36

answered Jan 16, 2013 at 13:26

ppeterka

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3 Comments

SDC Over a year ago

ah, but if you do it recursively, you might be able to get a StackOverflow error and brag about it on this site. Oh wait.... ;-)

ppeterka Over a year ago

Hmm, why did nobody comment spotting my two obvious mistakes (no $ in front of variable, and no incrementing of counter?)

Coder Web Over a year ago

Thanks a lot, I will try it and let you know

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