How do I put extra number at the end of username if duplicate

Question

Hard to explain, and let me show an example.

1. If username foo already exists in MySQL I want php script will allow it but to be foo1

Answer 1

First, lock the table so no other table will write to it at the same time. then do something like this:

$name = 'foo';
$first_name = $name;
$i = 0;
do {
  //Check in the database here
  $exists = exists_in_database($name);
  if($exists) {
    $i++;
    $name = $first_name . $i;
  }
}while($exists);
//save $name

---

Another method is to select all names in the table starting with "foo" and ending in a number and then finding the largest number. This can be done in SQL.

The first method is better for use cases with only a small risk of collision, since the pattern matching may be slow, but if you have a lot of collisions the latter may be better.