递归PHP函数未返回预期值

Question

I am trying to create a function that will create a unique username for each user stored in the database.

My plan was to create a username by concatenating the first and last name then check if this username was taken. If it wasn't just store it in the database and if it was then add a number on the end of it.

For example if ConnorAtherton was taken the function would next check ConnorAtherton1, ConnorAtherton2 until it found a unique username.

Here is the function (I have added some echo statements for debugging)

    function createUserName($username, $counter){

        global $fname, $lname;

        echo "\t\t\tUsername at Start - " . $username . "
";

        // connect to database
        require($_SERVER['DOCUMENT_ROOT'] . "/inc/db.connect.php");

        $stmt = $conn->prepare('SELECT * FROM users WHERE username = ?');
        $stmt->bind_param('s', $username); 
        $stmt->execute();
        $stmt->store_result();

        echo "\t\t\tUsername before loop - " . $username . "
";

            if( $stmt->num_rows > 0){

                //construct original name and try again
                $username = ucfirst($fname) . ucfirst($lname) . $counter;
                $counter++;
                createUserName($username, $counter);

            }

            echo "\t\t\tUsername after loop - " . $username . "

";

            return $username;
    }

Here is what it returns to the console

    Username at Start - ConnorAtherton
    Username before loop - ConnorAtherton
    Username at Start - ConnorAtherton1
    Username before loop - ConnorAtherton1
    Username at Start - ConnorAtherton2
    Username before loop - ConnorAtherton2
    Username after loop - ConnorAtherton2

    Username after loop - ConnorAtherton1

It returns the correct value after the loop (ConnorAtherton2) to begin with but I don't know why there would be a second value after the loop.

It returns ConnorAtherton1 and I need it to return ConnorAtherton2.

Any help is greatly appreciated.

Answer 1

The code executes as expected. What you are seeing is just the stack unwinding from the recursive calls.

You should modify your function to exit after the recursive call, by returning the result from the recursive call

     //...
    $counter++;
    return createUserName($username, $counter);
 }
 //... Rest of fn omitted