leveling up PHP algorithm - php

Question

I want some algorithm to make a PHP level up system I already made a system to level up people but what if people gained a huge amount of exp so they need to level up multiple times example of my code:
if(isset($_POST['id']) && isset($_POST['amount'])) {
$amount = $_POST['amount'];
$user = $_POST['id'];
$exp;$etnl;$newExp;$level;
`//select exp and etnl from DB
$result = DB::getInstance() ->query("SELECT exp,etnl,level FROM exp WHERE id = $user");
$result->setFetchMode(PDO::FETCH_ASSOC);
$row = $result->fetch();
$exp = $row['exp'];
$etnl = $row['etnl'];
$level = $row['level']
//c where to level up user or to add exp to his ep bar
if($amount + $exp > $etnl) {
$etnl = $etnl * 2;
$leftOvers = ($amount + $exp) - $etnl;
$newExp = $leftOvers;
$level = $level + 1;`
$result = DB::getInstance()->prepare("UPDATE exp SET exp=?,level=?,etnl=? WHERE id=?");
$result->execute(array($amount,$level,$etnl,$user));
} else {
$result = DB::getInstance()->prepare("UPDATE exp SET exp=? WHERE id=?");
$result->execute(array($amount,$user));
}
}`
`
but this system fails if the exp could level up a person 2 times any help or any new code? BTW etnl stands for exp till next level thank you

Answer 1

If you don't want to manually type out a level table like the other answer suggets you can also try doing your process with a recursive function:
$current_exp = 0;
$current_level = 1;
$to_next_level = 1000;
function did_level( $amount = 0 ) {
global $current_exp;
global $curent_level;
global $to_next_level;
$tmp_amount = $amount + $current_exp;
$tmp_amount_remainder = $tmp_amount - $to_next_level;
if ($tmp_amount >= $to_next_level) {
$current_level++;
$to_next_level *= 2;
$current_exp = $tmp_amount;
if ($tmp_amount_remainder > 0) {
// Level us up again.
did_level( $tmp_amount_remainder );
} else {
// Store the new level, to next level, and current exp
}
} else {
// Store the new exp amount
}
}

Answer 2

You have to get a table of levels which is basically a list of [exp, level] pairs. For example,
$level_list = [
['exp' => 0, 'level' => 1],
['exp' => 100, 'level' => 2],
['exp' => 1000, 'level' => 3],
// etc.
];
Then, you iterate the table starting from the end:
$i = count($level_list);
while($i > 0) {
$i--;
if ($user_exp >= $level_list[i]['exp']) {
// this is the level we need
break;
}
}
$target_level = $level_list[$i]['level'];
$target_exp = $level_list[$i]['exp'];