Generate new username and check if already exist - php

Question

I need to generate unique username automatically, I've created two functions, one to create a random username and the other one to check if the username is already stored in the database. Do you think these two functions can work?
function km_create_random_username($db_user_conn){
//set the random id length
$km_random_username_length = 6;
//generate a random id encrypt it and store it in $rnd_id
$km_random_username = uniqid(rand(),1);
//to remove any slashes that might have come
$km_random_username = strip_tags(stripslashes($km_random_username));
//Removing any . or / and reversing the string
$km_random_username = str_replace(".","",$km_random_username);
$km_random_username = strrev(str_replace("/","",$km_random_username));
//finally I take the first 6 characters from the $km_rnd_id
$km_random_username = substr($km_random_username,0,$km_random_username_length);
if(!km_check_random_username($db_user_conn, $km_random_username)){
return $km_random_username;
}
}
function km_check_random_username($db_user_conn, $km_random_username) {
$query = "SELECT km_user_username FROM km_users WHERE km_user_username=?";
$stmt = mysqli_prepare($db_user_conn, $query);
mysqli_stmt_bind_param($stmt, 's', $km_random_username);
mysqli_stmt_execute($stmt);
mysqli_stmt_store_result($stmt);
$rows = mysqli_stmt_num_rows($stmt);
mysqli_stmt_fetch($stmt);
if($rows > 0) {
km_create_random_username($db_user_conn);
}else{
return false;
}
}

Answer 1

To test that the code spots duplicates and then generates a new randon username do this.
Either empty the table km_user or record the last id value
Run the km_check_random_username() function twice manually passing the same username both time.
km_check_random_username($db_user_conn, 'ItsMee');
km_check_random_username($db_user_conn, 'ItsMee');
Check the table? Did it create the ItsMee username?
Did it create a random username after creating the ItsMe username? If it did, then it spotted the Dup and ran the regenerate phase

Answer 2

echo gen_random_username(10);
// generates jPMNfrQZil
function gen_random_username($db_user_conn, $length){
$chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
$random_username = "";
for($i = 0; $i < $length; $i++){
$random_username .= $chars[rand(0,strlen($chars)-1)];
}
if(!km_check_random_username($db_user_conn, $random_username)){
return $random_username;
}
}
// I didn't check this function, but I modified it to use the above function
// gen_random_username($x, $length)...
function km_check_random_username($db_user_conn, $km_random_username) {
$query = "SELECT km_user_username FROM km_users WHERE km_user_username=?";
$stmt = mysqli_prepare($db_user_conn, $query);
mysqli_stmt_bind_param($stmt, 's', $km_random_username);
mysqli_stmt_execute($stmt);
mysqli_stmt_store_result($stmt);
$rows = mysqli_stmt_num_rows($stmt);
mysqli_stmt_fetch($stmt);
if($rows > 0) {
gen_random_username($db_user_conn, 10);
}else{
return false;
}