recursive function in php class - php

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;
}
}
}

Answer 1

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

Answer 2

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.

Answer 3

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;
}